Sheltering beneath the streets of London, the company of a West End play find themselves isolated from their loved ones when a nearby terrorist attack cuts short their final night performance. Minds racing over past anxieties from the run, they contemplate life-and-death decisions within the claustrophobic confines of the theatre basement.

Alexander Armstrong and Richard Osman present a celebrity version of the general knowledge quiz in which contestants try to come up with the answers that nobody else could think of.