Five-0 investigates the murder of Professor Joel Cutler, whose body was found decomposing in a tub of acid at Oahu University. Evidence points to a number of suspects with motive to kill the professor, including his boss, a TA, and a student who was busted for cheating. McGarrett and Danny uncover a rare plant during a search of Professor Cutler's home; a plant that was thought to be extinct for 200 years. Their investigation takes them to the private island of Niihau, which is closed to public access. There they meet Brian Spector, a fellow researcher and partner to Cutler, who explains that he was working with Cutler and using the rare plant to potentially cure a very rare illness. This episode features multiple endings that viewers will choose between, with different suspects being guilty of the murder in the end. (The boss Devin Roth, the TA Bram Zelman, and the cheating student Tyler Brown are the three possible choices for the murderer.) In each case, Five-0 tracks the suspect to Niihau, where McGarrett and Chin Ho take the suspect down before he can bring any harm to Brian Spector.
Meanwhile, Kono is assigned to watch over Sang Min as he comes back to Oahu as a witness in a federal prosecution. When she turns him over to a DA and his HPD escort, Sang MIn gets the drop on them and escapes. Using a tip from Kamekona, Kono tracks Sang Min to his ex-wife's home, where he was waiting, hoping to catch one glimpse of his lost love. Kono sees how much he loves his family and tells him she can get him transferred back to Halawa prison if he behaves from this point forward. Sang Min gratefully accepts.
Danny also has to chaperone his nephew, Eric, who is visiting from New Jersey. Eric tags along as Danny and McGarrett investigate Cutler's murder, providing some useful insight as they gather evidence. In the end, it's a good bonding experience for the two.