Gerald, Cathy and Jimmy are forced to spend the summer holidays at Cathy's school. During a picnic, Gerald makes a discovery which leads them into many strange adventures.

Mabel, the housekeeper's niece at the castle, shows the children the jewel room. When she tries on a ring, her wish to be invisible comes true.

When Gerald tries on the ring, he can see the castle’s statues come alive at night. But when Eliza the maid puts it on, things start to go terribly wrong.

With the bailiff's help, Gerald and Mabel lock the 'Ugly-Wuglies' in a passage behind the temple of Flora. But the bailiff ignores the warning not to return to the temple.

When Jimmy tries on the ring he is transformed into a rich businessman and travels to London with one of the Ugly-Wuglies. However, Gerald is determined to get the ring.

Using the ring, the children all become statues and join in a feast with the other statues on the island. But when dawn breaks, they face a nasty surprise.