Grover is forced to take his family on the run when a dangerous mob boss seeks revenge for a 15-year-old case.
MacGarrett and the team support Danny and Rachel by determining what happened when Grace gets into a life-threatening car accident; Tani helps Koa when his rehab patient goes missing.
Harry Langford helps Five-0 investigate some murders that follow the plot of a fabled, unpublished crime novel from the 1920s; Tani and Junior's friendship takes a meaningful new turn.
Magnum and Higgins may have stumbled upon a serial killer, after a neighbourhood watch group asks them to investigate a shady character.
Magnum and Jin search for a skip-tracer at a Halloween bash, just as Katsumoto tracks an escaped killer who is headed to that same party.