Dawn is happy to be back in California. She and Sunny are spending all of their time at the beach taking surfing lessons and helping out with an after-school beach group for the younger kids. One day at the surf shop, Sunny points out a 20-year-old guy named Thrash to Dawn, who is one of the hottest surfers on the beach.
Dawn thinks he’s cute, but he’s not her type & too old for him, but she finds him fascinating & talks to him about surfing the next time she’s in the shop. She learns that Thrash has been surfing all over the world. As Dawn and Sunny leave the shop for their surfing lesson, he calls Dawn “Kelea” (which is the name of a Hawaiian princess). Sunny is convinced that Thrash likes Dawn, but Dawn isn’t buying it.
Several days later, when Dawn and Sunny go back to the beach, they get some bad news. Thrash’s mangled surfboard turned up on the beach and people think that he’s dead. The only person who doesn’t believe Thrash is dead is Gonzo, who is another regular surfer. There is a big surfing competition coming up and Gonzo is convinced that Thrash faked his death because he knew he wouldn’t win the competition. Dawn doesn’t think so especially when she finds out that Thrash’s surfboard might’ve been tampered with.
One night when Dawn, Sunny, and the kids from their after-school group are having a cookout, they spot a surfer way out into the ocean. Since it’s rare for anybody to be surfing so late in the evening, Dawn is convinced that it’s the ghost of Thrash out for revenge on whoever murdered him by tampering with his board. Dawn and the girls of the We Love Kids Club discover the mystery surfer again when they’re at the beach together, but this time he is performing a move that only Thrash is known to be able to do. Dawn discovers a new guy working at the concession stand who is tan with short, black hair which makes her suspicious.
As the surfing competition gets closer, there are a lot of accidents starting to happen to people at the beach; people who never fall off their surfboards get hurt become injured and one girl burns her eyebrows off while working the grill at the concession stand. Sunny ends up getting badly bruised in a surfing accident and her mom makes her give up surfing for awhile which leaves Sunny with more time helping Dawn solve the mystery.
When Dawn sees the concession stand guy again, she realizes that he’s Thrash in disguise. She confronts him when she catches him the surf shop tampering with Gonzo’s surfboard. Thrash said he wanted revenge on Gonzo who tampered with his surfboard in the first place. Dawn is able to talk him out of it and Thrash goes to the police. Gonzo is arrested at the surfing competition Thrash wins first place in the competition while Dawn finishes third place in her division. Thrash decides to use his prize money to surf in Australia for awhile, but before he leaves, he gives Dawn his snake ring.
Back in Stoneybrook, Marilyn and Carolyn Arnold are involved in gymnastics, but after Carolyn injures herself during practice at home, Marilyn feels responsible and decides that she’s not going to leave her sister’s side again.
For a while, the girls seem happy with the arrangement, but the BSC knows that it isn’t terribly realistic for them to stay that way, so they come up with a plan. They have a friend call each of the girls one day and invite them out somewhere, but only if they come by themselves. At first, Marilyn & Carolyn turn down the invitations, but then they decide that they would rather have fun than stick together all of the time.
Surf's up! Dawn is back on the coast just in time for the big surfing competition. She loves catching those waves and soaking up sun.
But soon Dawn has a mystery on her hands. Thrash, the most radical surfer around, has mysteriously disappeared. Only his bashed-up surfboard – and his ghost – remain.
Can Dawn solve her California mystery without the help of the BSC?