A man dressed in a costume plummets to his death beside a hotel pool and our 5-0 team investigates who wanted him dead. Our team identifies the victim as someone attending the local Cosplay convention, where attendees dress as their favorite anime or sci-fi character. He'd arranged to meet a woman he was having an online relationship with until her ex-husband showed up and beat him up. McGarrett and the team figure out the ex-husband didn't kill our victim and our victim may have been a case of mistaken identity. He was thrown from a room that belonged to a thief, who had been targeting several high-end houses on the island to support his party lifestyle. Clearly the thief had stolen something worth killing for. The find the thief who has no idea who's trying to kill him, but when the 5-0 team investigates his stolen merchandise, they find a flash drive hidden in a tourist "snowball" that has evidence of an old murder. Using the flash drive, the find the killer as well as solve the old murder.

Also, McGarrett meets Jenna Kaye, a CIA analyst on leave who offers to help him investigate Wo Fat.