You Can't Be Too Careful

Della Galway is the kind of woman who double-locks every door in the flat, checks both locks a second time, and still frets about it on the way to work. She's a prim businesswoman who likes her life exactly as she left it. Then a new roommate moves in, someone careless about security, and the small frictions of shared living start to build.

The setup sounds like the first act of a sitcom about mismatched flatmates. But it doesn't stay funny for long. The series' own description calls it a psychological tale of two women who share an apartment, one outgoing and irresponsible, the other shy and neurotic. Put those two temperaments in close quarters and the chemistry between them turns sinister. The threat grows in the space between the two of them, as their anxieties feed off each other and ordinary domestic life starts to feel quietly menacing.

Ruth Rendell and Ted Whitehead wrote the script, and Matthew Evans directed. Serena Evans leads as Della, the careful one, with June Barrie as Mrs Swanson and Jane Hazlegrove as Rosamund. The rest of the household comes from Debbie Chazen as Jackie, Paul Blair as Chris, Kate Binchy as Valerie and Simon Chandler as Gerald Adrian, with Gerard Fletcher as a police inspector and Les Doherty as Edward, the bearded man.

This is one of the standalone episodes, no Wexford in sight, and it works because the mystery is so small and so close. There's no locked-room puzzle and no body in the library, just two people sharing too much space and the paranoia that grows between them. For anyone who has ever had a flatmate who left the front door on the latch, the horror lands close to home. Being careful starts to look less like a quirk and more like the only sensible response.