Gappy invites three friends to keep him company at a bed and breakfast while his parents are attending a vampire conference. The excitement soon begins with the discovery of a secret passage under the house. With the help of some new vampire powers, he explores further, but a midnight adventure quickly turns dangerous when he is trapped underground.

Gappy is excited to travel with his best friend Pru to visit his cousins in the United Kingdom. His mother warns him to stay away from dangerous adventures, but after meeting two suspicious strangers in the sleepy Welsh village of Abergath, Gappy finds it difficult to obey. What are the two men up to, and what is the secret of the abandoned Penffordd Slate Mine? When Gappy and friends explore its underground tunnels, they uncover a shocking vampire plot before being captured and imprisoned in a rocky cell. Their only hope of escape is if Gappy can summon up a new vampire skill to rescue them...

The end of the school year should be a fun time, but for 11-year-old Gappy, it is absolutely horrible. First, he must fight for his life against a crazed janitor, and then his classmates and teachers turn mean. Gappy hopes things will be better at vampire summer camp, but dark forces are at work, and an Old Order vampire is after him again.