Shrive is a Middle English verb that means to prescribe penance: it survives today in the name of Shrove Tuesday, the date in the Christian calendar on which believers look inward to identify the sins they need to drag into the sunlight via confession and penitential labour.

In James Watkins’s soul-scorching, relentlessly riveting new episode of Black Mirror, it’s also the name of a virus-scanning app that 19-year-old Kenny (Alex Lawther), a waiter at an upmarket burger joint, installs on his laptop after his younger sister (Maya Gerber) accidentally infects it with malware.

Except of course scanning for viruses isn’t the half of it. With his webcam covertly activated, poor Kenny finds himself being filmed in a compromising situation which involves opening his laptop, locking his bedroom door and dropping his trousers. (He’s 19 years old, so your imagination quickly fills in the rest.) Afterwards his phone pips. It’s an anonymous text message written all in capitals: WE SAW WHAT YOU DID.