Laura Jesson (Celia Johnson) accidentally meets Alex Harvey (Trevor Howard) at a railway station on her way home from a neighbouring town. Both married with children, the pair begin to question their previously happy home lives when their chance encounter turns into a regular acquaintance and their initial friendship becomes a burgeoning attraction. Forced to hide their developing relationship from family and friends, the couple are almost discovered after being interrupted during a would-be tryst. Realising the impossibility of their situation, Laura and Alex must consider parting forever.

"Perfect parts include: the script, the lead performances, the steam trains, the music, the supporting performances, those accents, the bloody Refreshment Room, the end, the beginning, the middle." - Sophie Monks Kaufman, Little White Lies