Carl Matthews and Sally Thorn don't know each other, but they both get the 7.39 train, away from their suburban lives to their jobs in London, and one day their paths cross.
An argument over a seat, sees Sally and Carl start talking and suddenly their daily train journey becomes a lot more interesting…
But both have partners at home – Carl, his university sweetheart and best friend, Maggie as well as two teenage kids, and Sally, her fiancé Ryan.
Knowing they're playing with fire the closer they get, will Carl and Sally end up risking everything?
The 7.39, BBC1, 9pm
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