They were standing on the Valiant at 08:02.
Everything was finally back to normal, well... as normal as The Doctor's life can be.
"You still haven't answered the question, what happens to me?"
Right.
He hasn't really thought what he would do with The Master. He was a little busy, you know, saving the earth and stuff.
Oh well.
"You're my responsibility from now on, the only Time Lord left in existence."
Jack tried to tell him he shouldn't do that, that The Master was too dangerous, but he just wouldn't listen.
After all those years of loneliness and misery he finally got his friend back.
"It's time to change, maybe I've been wondering for too long, now I've got someone to care for."
The Doctor and The Master, in the TARDIS, just like it should be.
But then he heard a gunshot.
He looked at The Master first
Nothing, maybe a little shock on his face but beside that, nothing.
Then at Martha, nothing there too.
Jack.
He was lying on the floor, dead.
Of course, everyone in the room knew he couldn't die, but it wasn't the point at the time.
Lucy shot the gun, she was gonna hurt The Master.
Jack jumped in front of the gun to protect The Master.
Maybe he somehow forgave The Master, or maybe he knew how much it would hurt The Doctor if The Master died.
He looked at The Master again but he was looking on the floor.
He took him to The TARDIS and chained him there.
Time to say goodbye to Jack and Martha.
"The Face of Boe they called me."
Maybe a little shock is exactly what he needed.