The Brookedale Psychiatric Hospital is a crumbling institution which barely has enough money to remain open. Formerly a prison, it sits atop a warren of tunnels and sewage system viaducts. But Brookdale has a secret - a secret known by only one person. There's something living in the tunnels - something that's developed a taste for human blood...

Two twentysomething students, Alex and Zoe, are lovers. When Zoe's old boyfriend James returns from Europe, Zoe breaks up with Alex and returns to James. But soon Zoe finds out she's pregnant, and it's Alex's baby.