Torchwood and UNIT have consumed her world. She only becomes aware of this fact after Mickey is killed.
It was supposed to be a routine surveillance run on the Cardiff sewers. There'd been some Rift activity, according to Torchwood intel, and it was considered wise to run some checks. And then, a weevil in the dark... She always thought, if this dangerous life was going to take Mickey away from her, he would go out in a blaze of glory, sacrificing himself for the good of the whole world. Not a senseless killing in the sewer on a Thursday.
She takes some time off work. It's called "bereavement leave" but really, she knows it's retirement. She did a lifetime's worth of defending the Earth long before she joined up with UNIT. By this point, she thinks, she has more than paid her dues.
Except... now what? She is thirty-seven years old, a widow, and without a purpose. She could turn to practicing family medicine, but that... well, it doesn't appeal.
She finds herself in a quandary. She is Martha Jones-Smith, the woman who can't help but help people. Part of her feels that settling down into a private medical practice is the smartest way to go about it. The rest feels that after all she has seen, everything she has done, it is just too small a life for her. She knows what's out there, and part of her burns to still be part of that. Not in the way she was, though. She can't do that anymore. No more soldiers, no more regulations, no more procedure. There is no joy in that.
Every night, she hears the sound of ancient engines in her dreams. When she wakes, she dreads hearing them, because she has washed her hands of the Doctor. If he calls, she will come, because she must. She knows the others- Jo Grant and Tegan Jovanka and Sarah Jane and so many more- and she knows that any one of them will answer if the Doctor ever has need of them. They are all irreparably changed by that man, and no matter what terrible things they see, not one of them ever regrets it. But Martha doesn't think she can face him now, maybe not for a long time.
And then, one night, she does hear a sound. But it isn't the wheezing song of the most impossible time ship. It's a rap on her window.
She climbs out of bed and goes to the window in her nightgown. On the balcony outside her sixth-story flat, a woman stands. She is a strange woman, tall, with oddly shaped eyes, eyes so dark that- though she can't tell for sure in the faint glow of the streetlight- Martha thinks they must be jet black, in sharp contrast to her pale olive skin.
"What are you doing?" she asks, throwing open the window with no fear. "Who are you?"
The stranger smiles, and that is also odd. Her mouth twists upward in what ought to look like a smile, but really it's more of a sneer. "That's a difficult question. I've got a lot of names. Madame Xing. Laura Tobin. But he always called me Compassion."
"He? Who's he?"
"Don't be stupid. You know which he."
And she does. Because there's only one he it can possibly be.
"Did he send you?" Martha asks.
"Of course not. I doubt he even knows I survived the War. As far as I'm concerned, he can keep on not knowing. It makes it easier for us to clean up the messes he leaves behind if he's not aware."
"Yeah," Compassion says. "Us. You coming?"
Martha considers. It's tempting. But her time with UNIT has taught her- question everything. "How?"
Compassion smirks. "The Doctor drives a busted-up Type 40. I'm a Type 102. Get the picture?"
It takes her a second to work out what the other woman is implying. Then, her eyes widen. "You're kidding! You're a-?"
"Is that so hard to believe?"
"I suppose not. With everything else I've seen..."
"Exactly. You're not like the others, Martha Jones. You had the strength to walk away from him. Other people have before, but it didn't come from a desire to get away from all the danger and the heartbreak. You wanted to fight the good fight on your terms, not on his. We're the same that way. So what do you say? You coming or what?"
The next morning, when Tish pops by for tea, she finds an empty house and a note on her sister's pillow.