Ed and his friend Zack are on holiday in London. While Ed keeps noticing the particularly friendly and intelligent rats coming out of the cellars, Zack is more interested in the drugs on offer from rather more human rats.

Following a rat into an abandoned underground station, Ed finds himself on a weird journey into London's sewers and the forgotten River Fleet.

Here he encounters mystical owls and Victorian sewer workers, but also the power to take on the drug-pushers who threaten to destroy the city's youth.

In a stunningly dramatic climax worthy of Stephen King, Ed calls on ancient powers in a final confrontation with the evil drug baron.