On Valentine's Day, Tani and Noelani are held hostage during a convenience store robbery. Also, Five-0 investigates the murder of a Thai diplomat whose wife confesses to the crime, but Danny suspects she's covering for the real killer.

While Five-0 investigates a murder on a cargo ship where pirates impersonated the Coast Guard to board the boat, Adam finally gets the evidence he needs to take down the Island's Yakuza operation once and for all. Also, Quinn helps Noelani when she suspects that her uncle didn't die of natural causes.