A hitman with a double life and a fading memory is a terrific hook. Memory of a Killer opens with the kind of premise that makes you clear your evening: a killer you can almost root for, shades of Dexter, and the uneasy question of what happens when he can no longer trust his own mind.

Patrick Dempsey plays Angelo Doyle, a contract killer who keeps his work hidden from his family. An early-onset Alzheimer's diagnosis threatens to collapse the wall between those two lives. The tension is built right into the setup, and the opening stretch makes good use of it.

But a strong premise only gets a show so far. As the story moves toward its ending, the plotting gets away from what made it compelling in the first place. Instead of tightening the screws, it goes off the rails, leaving the early promise feeling frustratingly unfulfilled.

There is still something here for crime-thriller fans, especially if the idea of a good samaritan hitman appeals to you. Just go in knowing that the finish does not live up to the start.