Martha might think that, and she might also think (probably did think) that he was being too overly protective or concerned about things. But the Doctor would much rather keep Jenny in the dark about the Master if it meant she wouldn't do something like try and face him herself.

Unfortunately now he had to try and come up with something to tell her, otherwise she'd do exactly that. And he wasn't sure he'd much like the results of her running up against the other Time Lord.

He followed Martha out of the bathroom and draped his shirt over the arm of the couch again, settling down onto it with an almost mulish expression. It was hard to tell which out of him or Jenny was sulking more.

"I suppose I owe you an explanation," he said eventually.