Two Americans college students, David and Jack, are backpacking across Europe when they are savagely attacked by a werewolf. David wakes up in a London hospital to be told he has been in a coma for three weeks and his friend Jack was killed. His penis also has maintained a permanent erection since the attack. Soon David starts experiencing horrible dreams, and his dead friend comes to warn him that he will turn into a werewolf. A kind English nurse takes the distraught young man to her flat. Soon David discovers the curse is real and goes on a rampage through the streets of London as a bloodthirsty werewolf.