Carl Matthews is stuck. At the age of 45 his life has become routine. Every morning Carl fights his way onto the 7.39 train where he sees the same unhappy faces doing the same daily commute into Waterloo. Happily married to his best friend from college, Maggie, with whom he has two healthy, if sullen, teenage kids, life for Carl has become predictable.

Sally Thorn has recently moved out of London, where she still works as the manager of a health club. But she's unsure if she likes her new suburban life, or the prospect of marriage to Ryan, a handsome personal trainer. Ryan is desperate to start a family, get married, settle down. Sally secretly wonders if he really is the man for her. Not that there's much time to worry about these things, not while she's running to catch the 7.39.

Over a fight for a seat Sally and Carl begin talking and suddenly their daily train journeys become a lot more interesting.

The 7.39 is the story of how even the most predictable of lives can, in a fleeting moment, dramatically change course.