The Sibunas uncover the details of the secret ceremony in a very special place. They rush to rescue Harriet Denby, but discover she's gone. Jerome's love life is in a tangle.

The Sibunas learn that they must perform the ceremony themselves. With news of a school open day, it's the perfect opportunity to sneak out the tank....or is it? Meanwhile, Jerome's double life catches up with him.

The Sibunas make it to the Crypt with the tank and begin their ceremony, but Denby's discovered Frobisher has gone. Can Sibuna complete the ceremony before the adults find them?