Fitz is in trouble. He's accidentally got himself hired as an assassin while trying to emulate James Bond. And he's upset Bigdog Caruso, the unofficial Canvine leader on Vega.
Sam is in trouble. She's become involved with the key witness to a murder, and the witness has vanished.
The Doctor, meanwhile, has been roped in to help with investigations into robbery, sabotage and the murder, as well as to sort out Fitz's problems, Sam's problems and the President's safety. He's in his element.
And if they should get bored, there's a hitman on the loose, monsters roaming the station corridors, an exhibition of art by a painter who depicted his own death, and the opera.
This is another in the series of original adventures for the Eighth Doctor.