A birthday present for the incomparable Rachael, in response to her prompt (which I'll reveal at the end of the story). Happy birthday, Rachael! You are fabulous and deserve great things and, at the very least, you deserve any story you want on the anniversary of your birth.

INSANITY

Insanity: doing the same thing over and over again and expecting different results. (Attributed to Albert Einstein)

Mark moves down there for the sunshine. He calls her to say I almost died today and she holds Henry close and winces into the phone and remembers how fragile life can be. His injuries need therapy and time and they don't need the dampness of Seattle. There's a shoulder expert at St. Sebastian's, there's a gorgeous rental on the beach, and everything makes sense until she explains it to Sam.

"Why L.A.?"

"I told you."

Sam frowns, reaches for Henry and she hands him over. "I think you already have a lot to focus on."

"I'm not going to operate on him, Sam," she laughs. "He's not pregnant. It's just that this is the best place for him to recover."

"He's not moving in with us," Sam calls after her, and she laughs again.

"You have nothing to worry about," she tells him, warms Henry's bottle and reaches for her son. Sam reaches for the bottle instead and she lets him do the feeding. She smiles at her two boys, twists the diamond on her left hand. She's so lucky.

He looks thin when she sees him, too thin. There are bandages and he's greying more around the temples than she remembers. She hugs him carefully. She knows about Lexie, knows about Derek's hand, about Arizona's injuries. She knows everything so he doesn't need to tell her, that's what she reassures him.

He says thank you and tries to smile. Then he sees Henry and his smile turns real.

"You're a mother," he says quietly.

She turns her face up to him. His eyes look soft, faraway.

"You're punishing me because I wanted the baby? That's it?"

"I'm leaving. Don't act like you're surprised, Mark-"

"I want you to stay!"

"No, you wanted the baby."

"Not just the baby, Addison."

"No." She shakes her head, hard. He reaches for her but she brushes him aside. "I should never have - you haven't changed. You can't think past your next lay."

"That's not true. You're the one treating me like - two months and you're done? That's it?"

"Richard said Derek's seeing someone, in Seattle-"

He raises his voice, and she flinches. "You're seeing someone here!"

"I - I want to talk to him, Mark. He's my husband."

"If he wanted to talk to you, he'd return your calls."

"Can you blame him? After what we did?"

Mark looks grim. "Yeah. I can blame him."

"Mark-"

"Addison, come on. Don't run away. Stay here, where you belong, and we can fix this-"

She snorts. "That's rich."

"Is this because of Char-"

"Don't say her name," she snaps.

"I'm sorry, Addison, I told you I was sorry. You're married, okay? You cheat on me every goddamned day you stay married to that-"

"Don't talk about him either!" She knows she sounds irrational but can't help it.

"You're going to protect Derek now? You think he'd do the same for you?"

"I guess I'm going to find out."

"Don't do this, Addison."

"I'm going," she insists.

"Addison-"

She closes the door behind her, harder than she needs to, wants him to remember her straight-backed and angry because she's not going to cry. She presses her forehead to the wall next to the elevators, says good-bye to this hall.

Part of her wishes he'd follow, but as her steps echo - alone - on the damp sidewalk, she knows he won't. He hurt her and she thinks she might hate him but he's Mark. He doesn't push her.

She does cry, though. She cries for him, surprised at the amount of naked sadness. Or maybe it's for everything: the future they won't have, the past she's screwed up, and the missing piece of both of them. She cries walking home, in the rain, and when thunder cracks overhead it feels like the sky is crying too. She cries in the shower, hot water pounding against her flushed skin, and tries to forget the last time he took her in there, her back against creamy marble, her heels digging into his thighs. She cries in bed, holding a pillow to the emptiness in her midsection.

And then, as Montgomeries do, she stops. She washes her face, ices her swollen eyes, applies careful layers of makeup. Silk, fur, heels. Door, stoop, taxi. By the time she gets to JFK her face is an icy mask, just the way she likes it. By the time the wheels touch down in Seattle, she can't feel anything at all.

Sam asks: "Does he need to come over so often?"

Addison just shrugs. Mark has a rental apartment and Addison has a beach house. Mark has injuries that scare her when she sees them and Addison has a rosy-cheeked infant who makes everyone smile. Sam should understand, because among them they have twenty years of history.

Mark falls asleep on the couch and Addison covers him with a blanket. He wakes up screaming and she drives him to the practice, introduces him to Sheldon. They take drives because walking makes him tired. He tells her about Lexie and she listens. They sit in the sand, once, his head in her lap, and when he cries she cries too. Whatever else she was she was a doctor and a younger women than Addison and she shouldn't have died in a forest while Mark watched. He goes to see Sheldon again. Then he starts going regularly.

He's happiest when Henry's around, so he and Addison walk him often on the beach. He misses Sofia, Addison knows this. Callie's going to bring her for a visit, once Arizona's stronger. Mark could fly back but he's hesitant.

She drives him to physical therapy, encourages him to call Derek. He must miss you. They call together. Derek's in surgery, and they share a smile because nothing really changes even when everything does.

"Do you want to fly back?" she asks when he's been living in Los Angeles for three months. He declines, says the flight's too long and his joints will get too stiff. It's a catch-22: he's too weak to fly commercial and too healthy to be medevac'd. Or so he says.

They watch Henry gurgling with pleasure on a beach towel, waving chubby feet in the air.

"You're working less," he observes and she tells him about what it's like to spend time with Henry, how lucky she feels that she can have a flexible schedule, enough time to breathe in every last sweet baby scent in his ever-thickening hair, to see how he responds to mashed bananas, to the puppy he sees on the beach, to Amelia's welcoming embrace.

There's a note of longing in his voice; she knows he's anxious to be able to work again. The injuries to his chest and back are improving steadily, she knows this. Physical therapy is making him stronger again. She knows he's getting better when, six months in, he meets Charlotte for lunch. She sees them at the hospital, raises her eyebrows at Charlotte.

"I always told him there was a place for him here," Charlotte shrugs.

"I'm not in fighting form," Mark mutters, and Addison knows it takes a lot for him to say that.

"So get there," Charlotte snaps. "And don't take all day about it. I have a hospital to run." And she stalks off on impossibly high heels.

Addison and Mark both watch her walk away.

"I like her," Mark says finally. Addison swats him with the patient file she's holding.

"Not like that," he says hurriedly, and she smiles at him, deciding she'll know he's truly all better when he does like Charlotte - or someone else - like that.

He's leaving an appointment with Sheldon just as she exits Cooper's office with Henry in her arms, fresh from his nine-month well child visit. Henry's sulking from his shots, and Addison's cooing to him and doesn't see Mark until she bumps directly into him. He grasps her arms, steadying her and Henry, and she pulls back nervously. "Did I hurt you?"

"No," he says sharply. Then, in a more even tone: "Addison, I'm fine."

She looks at Henry, anywhere but at Mark.

"Physically anyway. Look, just - I'm not made of glass. Okay?"

"Okay."

"Can I hold him?" he asks. She nods and he reaches out his arms, waiting for Henry to respond. Henry looks up, smiles a gummy baby smile interrupted with brand new teeth, and reaches chubby arms out in return. They walk to Addison's car in companionable silence.

Henry's tired so they end up at Addison's house, putting him down for a nap while Mark orders takeout. They take the baby monitor to the patio and watch the waves. Addison gets updated on physical therapy and on Sofia, and Mark - wincing only slightly - gets updated on wedding plans.

"Don't you have any girlfriends you can talk to about this?"

"I'm marrying my best friend's ex-husband," she deadpans, and they both laugh, breaking the tension.

They eat pad thai and sip wine while the sun sinks into the sea. Addison realizes, after Mark leaves and she's rinsing the wine glasses and checking on a sleeping Henry, that she hasn't spent this much time with Mark in years. Not without an agenda or an emergency. Not casually or organically, the way it is now. It reminds her, she realizes, of the time in New York before their affair started, when he'd drop by the brownstone or take her to dinner after work. The rhythm is gentle, with no pressure, and she's both grateful and surprised. Whatever it means - that they've grown up, that they've grown over each other - it must be right.

Callie flies down with Sofia. She's impressed with Mark's progress, and Henry is impressed with Sofia. He's crawling now, never faster than when Sofia toddles through the house or across the patio.

"They're cute together." Callie slides onto one of the deck chairs, crosses her long legs. She has a glass of wine in her hand, a relaxed smile on her face.

Sofia's climbing all over Mark, and he brushes off both Callie and Addison when they warn him to be careful.

"Daddy better," Sofia pronounces.

"That's right, sweetheart." Mark sweeps her onto his lap and when Henry crawls closer he leans down - if it hurts his ribs there's no indication - and scoops Henry onto his other knee. Henry reaches for a fistful of Sofia's dark hair.

"Oh, I have to get a picture of this." Callie fiddles with her iPhone. "They're going to go crazy over it in Seattle." She snaps a few shots, then shoots Addison an amused look. "Mark's still disgustingly photogenic, I see."

Addison can't help smiling.

"You get in now, Addie."

"Me?"

"Yeah, get in there." Callie motions her toward the couch.

Addison glances around uncertainly. "I don't think I-"

"Hurry up, my fingers are getting tired."

Addison settles on the couch a foot or so away from the three of them. Henry turns to her with a wide smile on his face and she can't resist planting a kiss on his cheek.

"Oh, perfect!" Callie claps her hands. "But I couldn't get everyone in. Move closer."

Addison inches over.

"Closer, Addie!" Callie gestures impatiently.

Sighing, Addison slides all the way over until she's sitting up against Mark's warm bulk. At Callie's glare, Mark lifts one arm and Addison, not immune to the glare either, tucks herself under it.

"Much better." Callie takes a few more pictures. "This one's a keeper."

"Why are you here?"

"For one reason: to take you home."

The words haunt her. She sits on the trailer's excuse for a couch, a blanket around her legs, a cup of tea in her hands. Neither trick is working to warm her. Derek's asleep but she knows better than to try to crawl under the covers with him for warmth. Maybe it isn't warmth she wants, it's something to grasp onto her. The blanket, holding her down. The tea, grounding her. Because if she's honest with herself - and oh god, how hard she has to try sometimes not to be - it's killing her not to be at Joe's right now. He's sitting there alone, waiting for her. He's Mark: he doesn't push her. He's not going to come to the trailer and grab her, sweep her back to New York with him. He'll wait for her and he'll hope and she'll hurt him again.

"Addie?"

She glances over, trying to keep the hope out of her voice. Derek's up, sleepy-eyed, his head lifted off the pillow. He's actually noticed she's awake. Maybe he sees how she's struggling, how sorry she is that Mark's coming out here hurt Derek. Maybe he'll ask her if she's okay, or even tell her that he loves her - he hasn't done that yet, and -

"You didn't turn off the stove light."

"Oh." She glances toward the tiny kitchen. "Sorry, I'll-"

But his head is already back on the pillow, eyes closed.

She swallows tea and wishes she could cry. But she knows the rule: tears should be shed only in the privacy of one's own home. And this is not her home.

Mark's a little down after Callie and Sofia leave. She's finding herself more attuned to his moods these days - maybe it's because she sees him so often; he's at the practice, meeting with Sheldon. Or he's at St. Ambrose, slowly starting to build a temporary practice even as he builds up his own strength. She's going to miss having him around, she can admit. His lease will be up in a few months. He'll go back to Seattle and they'll see each other less than sometimes. Emergencies or - maybe she'll invite him to the wedding.

Maybe.

She walks with him on the beach one evening - it's good for his legs, the uneven texture of the sand strengthening his muscles without straining them. He walks barefoot so she does too.

"How was your walk?" Sam's holding Henry in one arm and his blackberry in the other when she gets back.

"It was nice." She holds her arms out for Henry and he reaches for her, giggling that baby laugh that slays her every time.

"Mark's been over here a lot."

She balances Henry on her hip, busies herself smoothing his little shirt along his back while she ponders Sam's comment. "Well, Callie was staying with us," she says finally. "And I think he misses Sofia, so he-"

"Henry's not a replacement for Sofia."

She frowns. "I know that, but-"

"Has he tried anything?"

"Tried anything? Sam, what?"

He shakes his head. "Never mind. I'm a patient man, Addison, but please let's not make things any harder."

She's genuinely confused. "Sam, I don't-"

"Never mind." He takes Henry from her arms and kisses his cheek. "I'll put him to sleep so you can shower." His gaze skates over her - she's in a tank top and running shorts - "-and maybe slip into something a little less comfortable."

She would have liked to put Henry down herself - she missed him today and she loves hearing his sweet sleepy breathing as he drifts off - but she's grateful for Sam's help and knows things would be a lot harder without it.

"Are you upset with me?" She asks tentatively when he's climbing into bed next to her. She's pulled the covers up to her chin.

"No, baby, why do you ask?"

"Because - well -" but she doesn't want to borrow trouble so she casts him a sideways smile and lowers the silk sheet just enough to show him that she's not wearing anything beyond a pair of white silk panties. His eyes widen with surprise, then approval, and then everything disappears as he rolls on top of her and she lets him remind her just how good to her he can be.

Mark's over later in the week; she puts Henry to bed while he takes a call on the patio. His body language through the glass door screams good news and she heads outside as soon as he hangs up.

"What's going on?"

"That was Callie." Mark's smiling, the broad grin of someone who can't help himself. Oh, I recognize that look.

"What did she say?" Addison prompts.

"Arizona got an offer at Children's Memorial. Callie kept saying she didn't like what the dampness was doing to her joints, and they're taking it. They're moving here."

Addison's mouth drops open. "They are? That's - Mark, that's incredible!"

She hugs him without thinking about it, and he hugs her back. His arms feel so familiar. Part of her wishes she could stay.

"So that means-"

"It means I'm not going anywhere." He releases her and she takes a step back.

He's staying.

"Addison?"

"Yeah?"

"Do you know a good realtor?"