Brady and Boomer try to recover a lost medallion that is sacred to the island but Brady, along with Mikayla, is kidnapped by the Tarantula people. Meanwhile, Lanny embarrasses Mason by showing an old workout video that features him in it.

The kings must perform for the islanders at the Annual Harvest Festival, and Boomer can't wait to show off his singing skills. Brady knows Boomer has a horrible voice, but doesn't have the heart to tell him. When Brady's plan to protect his brother from humiliation backfires, Boomer discovers Brady is a terrific singer and arranges for Brady to sing to the kingdom.

When the Kings' over-the-top spending causes a monetary crisis on Kinkow, Lanny has the islanders pay mandatory donations to the kings. Buying time until they find a better solution to fix the crisis, Brady and Boomer disguise themselves as bandits Sirocco and Sirocco Taco, stealing the kingdom's donations and returning the money to the public. With criminals on the loose, the Kinkowians start to get angry and the kings must find a way to restore the island's fortune, capture the criminals and win back their kingdom's support.

Boomer opens the teen hotspot of his dreams and hires Brady as his assistant. When Boomer fires him, Brady spitefully opens his own club across the way inside a crypt upon being guided there by Lanny. When Brady performs a new song for the crowd with the lyrics having been provided by Lanny, the club is overrun by zombies that have been awakened by the song. Now it's up to Boomer to put his differences aside and rescue his brother.