St Sebastian's School in Grimesford is the pits. No, really it is. Built on the boggy remains of a medieval plague pit, this once proud school's dodgy nineteenth-century foundations are causing it to slowly subside. Every year it sinks a little further into the ground, and every year the ghosts of the plague victims underneath become more disgruntled. All they want is to rest in peace, but during term time all they hear is the clatter of hundreds of pairs of high school kids' feet overhead. The ghosts - egged on by their spooky ringleader, Edith Codd - decide to get their own back, and they're willing to play dirty. Really dirty. They swarm into the St Sebastian's sewer system and start to kick up a stink the only way they know how. Popping up through pipes and taps, they invade the school, morphing into monsters and zombies, performing possessions and hauntings, and generally causing as much mischief as in inhumanly possible. But the ghosts haven't reckoned on a new kid and his mates in year seven. Can James and his friends get to the bottom of the problem and flush out the ghosts, or will every terms at St Sebastian's be plagued with misery?