Ben is on a school trip. So is Jasmine. What they don't know is that not everybody in the theatre is there to watch the play and, in fact, they'll never get to see it . . .
There is panic at the Barbican when the fire alarms start wailing, but the strangely silent theatre staff, trap them inside the building rather than letting them out to safety. Ben, Jasmine and their classmates soon discover that there's no fire - what's happening is much weirder, and much scarier.
Strange spider-like creatures swarm through the building attacking people and turning them into vicious killers, and the kids have to run for their lives. But barricaded in an office, with these creatures waiting outsde for them, the children realise they're stuck. Will they ever get out? And, more importantly can they trust each other . . . ?