The Thundermans head to Hawaii for a vacation that they planned. However, when Phoebe accidentally absorbs the evil powers of Dark Mayhem, she becomes determined to complete his plan for world domination and must be stopped.

Tired of hearing tales of Hiddenville's legendary mayor, the kids use a time machine to travel back 60 years to disprove the myths; but when they inadvertently alter the past, the effect spells disaster for their hometown.