When the CIA informs McGarrett that his mother has gone rogue on her undercover mission and may have killed her partner, Steve goes to Mexico to bring her home and prove her innocence.
McGarrett joins Junior and his SEAL team on a mission to capture an elusive person who is holding his mentor hostage; Gerard Hirsch and Kamekona help Grover and Tani on a murder case involving art stolen by Nazis during World War II.
As Doctor Lucien Blake and Jean prepare their upcoming wedding, tragedy strikes one of Ballarat's most prominent families; they are suddenly faced with three murders, two weddings and a funeral.