THE 7.39 is a two-part TV film written by David Nichollas, the man behind blockbuster romcom One Day.
It stars Sheridan Smith and David Morrissey.
Is The 7.39 a repeat?
The BBC will air episode one of The 7.39 TONIGHT (September 21) at 9pm.
The second episode will be shown the following night at the same time.
This is not a repeat, nor an extension of the series - it is just a reshowing of TV film.
It will be available to watch again on iPlayer once aired.
Who's in The 7.39 cast?
As well as having a big writer behind the show, lots of familiar faces feature on screen.
David Morrisey stars as Carl, one half of the infatuated couple.
He is known for being an actor who prepares for his roles by living some of his character's experiences in his own real life - when playing a chef once, he worked in a kitchen to get into character.
Sheridan Smith plays Sally, the manager of a health club.
Sheridan is well known across TV and theatre, having starred in Cilla and Gavin and Stacey.
Olivia Coleman plays Carl's wife while Sean Maguire stars as Sally's partner.
What is The 7.39 about?
Warning - spoilers!
The 7.39 is about two commuters getting the 7.39 train, meeting and beginning a passionate love affair.
The first episode looks at how it begins, showing Carl dissatisfied with his attentive wife and unappreciative kids.
He begins chatting to Sally on the train, who is engaged.
They begin speaking as friends, but soon look forward to their commutes just so they can speak again.
Carl ends up joining the health club where Sally works, so he can see more of her.
THE ENDEastEnders boss reveals why Chantelle was killed in conclusion to abuse storyline
BOOZE-HOOEmmerdale’s Gabby Thomas left drunk and alone after being shunned by her family
ice packDancing on Ice drops first big hint at four celebrities joining 2021 line-up
TRAGEDY PREDICTED EastEnders fans reveal clue showing how Chantelle would die 9 months ago
END OF THE GRAY11 huge EastEnders plots for next week including Kheerat exposes Gray
HEY JUDECorrie casts Michelle Keegan's son from Brassic as Nick Tilsley's secret son
One night their train isn't running, so they book at hotel room and begin their affair.
The second episode focuses on the repercussions of the affair and how they are in love.
Part one airs TONIGHT (September 21) on BBC One at 9pm.