The HPD system is hacked and the Five-0's confidential informant is murdered. The team enlist the help of the recently imprisoned hacker Aaron Wright to solve the case.
The team investigate the weapon used in the murder of a scuba diver. Analysing the weapon found on the ocean floor they realise it was used in a another recent murder. McGarrett prepares to propose to Catherine.
McGarrett and Danny get Tani Rey to join the task force when a hacker manages to let out a dangerous arsonist from prison.
The stunning truth about a decades-old disappearance of four school boys comes to light when a neurosurgeon is murdered right before a procedure; someone steals McGarrett's car.
The team go back to school when a college professor is murdered, with Danny posing as the professor's replacement.
