After a bank closes on Easter Saturday, three men burst in to clean out the safe. To help ensure a scot-free getaway, the trio locks the bank manager (Colin Gordon, The Pink Panther) and his cashier (Ann Lynn, A Shot in the Dark) in the vault.

Because the vault is airtight, the looters risk their simple robbery being upgraded to a double murder. One of the thieves (Derren Nesbitt, The Playbirds) has enough of a heart and soul to return to the scene of the crime to free the employees before they run out of oxygen. Through a series of extraordinary circumstances best left to your discovery, that proves easier said than done.

All of 80 minutes, Strongroom qualifies as a ticking-clock thriller, even though director Vernon Sewell (The Blood Beast Terror) approaches the material with a low-key manner typical of the British film industry’s buttoned-up B pictures of the era. In the second half, it even takes something of a sojourn into pavement-pounding detective work to allow a police sergeant (John Dearth, ITV’s The Adventures of Robin Hood) to assemble the puzzle. It’s confidently taut without breaking a sweat.

None of that is to be taken as a weakness. But if you’re looking for one, allow me to point you to the bank manager unwilling to dial or answer a telephone on his own, because that’s what women were for. Anyway, Stronghold: economic storytelling without surrendering anything in return, as one hell of an ending coldly corroborates. —Rod Lott