The Doctor had known jealousy before; it wasn't a foreign concept to him – but it always surprised him. Maybe because he'd been around long enough for him to know it was a petty emotion, a useless emotion, a baseless emotion and yet, he felt it churn through his veins, turning his stomach, pumping at his hearts, and searing the skin at his collar. And despite every logical bit of his brain yelling at him to accept the sight before him, to ignore the feelings he was experiencing, to walk away and have a bite to eat and wait for her back at the Tardis, he knew that jealousy was nothing if not illogical.

And it definitely made one do illogical things.

Like stand awkwardly behind a shield of multi-colored shawls to watch the way she smiled at the strange man who held a dress in his hands, discussions of her making the purchase gone and replaced with flirtatious banter and unexpected laughter. It was what had caught his attention in the first place: her laugh, a smidge louder than it generally was, and just a tiny bit… more feminine?

He couldn't put his finger on what had made it different, but when he'd glanced over, she was just finishing running a hand over the salesman's as he held a sparkling red dress up for her approval. Any of his other companions and he imagined he'd have gone over; he'd have embarrassed her; he'd have scowled at the dress and he'd have beckoned her to continue walking with him because to him it would have been a waste of time. A bit of a frivolity, the purchase of a souvenir in a time and place they ought not be.

But Clara gave him pause because he considered why she was laughing; why she was examining the dress even though he knew she'd never afford it; why she'd continue talking to the awkward man with the scraggily beard and the oversized eyes and the nose… the Doctor huffed. He dropped back behind the curtain of colors as she turned in his direction, pretending to examine a necklace on a tray in front of a woman who eyed him knowingly.

"Where do you travel from?"

His voice was deep, seductive, tinged with an accent that made the Doctor think of a leprechaun, but he could hear the soft chuckle she gave as she told him, "Quite a ways away, actually."

"Do you travel alone?"

There was a pause in which his jaw fell slightly and his brow furrowed because it was a dangerous question to answer. What if he was trying to decide if he was going to kidnap you; eat you; rip you apart; turn you into a robot for fun to be rented out at parties – of course you're not alone, Clara Oswald, and don't you dare… "No, with a fellow, should be wandering about; surprised he's not here, actually…"

"A fellow," he cooed teasingly.

Clara laughed again, "Oh, no, it's not like that." It most certainly isn't. "He's a good friend."

Setting the necklace down, he frowned. Of course he was a good friend. Why did her calling him a good friend sink like a rock in his stomach? He knew exactly why. The Doctor took a long breath and straightened as the man asked, "Maybe your good friend would appreciate you better in this dress."

There was silence and the Doctor chanced to peek back around the shawls to see her looking shyly to the ground before telling him, "I don't think a dress is what would get his attention," then her face stilled as she spoke to the air beside her, "Beginning to wonder whether he chases skirts at all."

"Maybe you need a better fellow to travel with," the man offered, raising a finger to lift her chin and slipping it away when she met his eye.

Clara took a small step back and muttered, "I should really find him; tends to get himself into trouble."

Shifting back, the Doctor watched her zip past, some odd look on her face he'd never seen before, and he glanced back around the corner, to the man now hanging the dress back up on a rack. Walking swiftly towards him, he gestured with a nervous smile and declared with a wave of his psychic paper, "Quality control, from the department of linens and… things – need a few samples to take back to the bosses, you understand…"

When he'd returned to the Tardis, he hid the box, too afraid to admit he'd been watching. Watching, he knew, meant he'd been too afraid to approach. Not approaching, he knew, meant he'd felt something other than the nonchalance he should have been feeling. Feeling something, he knew, would lead Clara's mind to the question of what would keep him standing a few feet away, watching with a scowl.

Clara's mind would know, instantly, that he'd been jealous.