An English lawyer arrives in Hawaii just to hand Steve McGarrett a letter that Doris instructed to deliver four months after her death, containing a ciphered message, which he ignores. The Five-0 task force investigate a botched home invasion/attempted kidnapping, where a good Samaritan busboy stepped in and killed one of the robbers, saving a mother and kid son, then vanished. He lived under a dead man's identity, actually being decorated war hero Lincoln Cole, who went AWOL from the Marines. The shot robber's brother, drug boss Hector Acosta, seeking revenge on Cole, has the mother and son that he rescued earlier, captured demanding an exchange for Cole, who is taken into Five-0 custody for his own protection, but surrendered to the Marines MP as AWOL, only to escape and meet the deadline, only not alone. Danny and Tani worry about Steve after he received the cipher from Doris, McGarrett contemplates leaving Five-0 after ten full-on years. Lincoln notices the cipher letter and offers to have it decoded.
—KGF Vissers