Jerry recovers after being shot. Tani and Junior attend the opera. McGarrett's date with Brooke gets interrupted by a call from Danny, who set them up. A mob boss gets assassinated at the opera. Tani and Junior encounter the shooter. McGarrett wings him but he escapes after an extended chase. The assassin appears to have a military background. Grover interviews Wes Cullen, whose stolen car was used by the shooter. Sgt. Quinn Liu of CID is looking for the assassin and has a showdown with McGarrett and Danny. She identifies him as Tom Kendall, a missing veteran. Tani and Junior discover a doctor is missing near a blood trail at a hospital. They track the doctor's car to a warehouse, where Kendall had shot himself when cornered. His accomplice is missing. McGarrett texts from Kendall's phone, and finds out there's more hits planned. Adam addresses a gathering of mob bosses looking for a suspect. Quinn barges in on the meeting. She tells Tamiko's father Masuda he is the next target. The sniper Sanders takes out several gangsters. Quinn and Adam get Masuda out although she gets shot, but Sanders escapes in a monster truck. Both Kendall and Sanders were being treated in a study for PTSD. Someone is targeting the members of an old loan-sharking gang. Sanders' next target is Zhang, the gang's old boss. McGarrett and Quinn pursue Sanders through Zhang's house. McGarrett and Sanders battle, then Quinn kills him when he won't drop his gun. Cullen the realtor financed the PTSD study and recruited the assassins. His wife and daughter were killed when his car exploded. McGarrett keeps Quinn on the Cullen investigation after she's been demoted from CID. Jerry tells McGarrett he's leaving Five-0 to write a conspiracy book. But he's willing to remain a consultant.