Alex O’Loughlin as Lieutenant Commander Steven “Steve” J. McGarrett, USNR- (United States Navy Reserves) is the older brother of Mary McGarrett and the son of Doris McGarrett and John McGarrett.
In addition, Steve is also the leader of the Hawaii Five-0 Task Force and partner to Detective Sergeant Danny Williams with the H50 team including Detective Lieutenant Chin Ho Kelly, Officer Kono Kalakaua and also Lou Grover .
The eldest of two children, Steve McGarrett grew up with his younger sister, Mary, and his parents, his father, John and mother, Doris in Honolulu, Hawaii.
He was named after his grandfather, Steven McGarret, a navy ensign on the battleship “USS Arizona, was killed on December 7, 1941 in the Japanese attack on Pearl Harbor. He was killed when the Arizona was struck by a 1,700 pound armor-piercing bomb which ignited her forward magazine. 1,177 of her crew were killed and their bodies, along with Steven’s, still lay inside the Arizona which has become a memorial for Pearl Harbor.
When Steve was fifteen or sixteen years old, his mother was killed by a drunk driver in a car accident (although it was later to be revealed as a homicide) but she survived revealing after Season 2 that she is Shelburne. This left his father John to raise his two children alone.
Unknown to them, their father was investigating the Yakuza and Hiro Noshimuri (which ultimately got their mother killed).
Fearing for Steve’s and Mary’s safety, John sent Steve and Mary separately to the mainland while both children remained unaware of what was really going on at the time.
After attending the US Naval Academy in Annapolis, Maryland , graduating at the head of his class. Steve then joined the Navy SEALs, graduating at the head of his class , and served for six years (four years in Afghanistan) before transferring to the Naval Intelligence Corps. He had been pursuing terrorists Victor Hesse and his brother Anton Hesse for five years. During this time, he learned to speak Mandarin Chinese.
In the pilot epoisode,
Steve is transporting a prisoner in Pohang, South Korea. Anton Hesse, who McGarrett has been tracking along with his brother Victor for over five years, is an international arms dealer. Hesse taunts Steve just as his cell phone rings and Steve looks to see the caller ID is his father John. He answers the phone to find Victor Hesse on the other end. Victor explains that Steve will release Anton and his father will live. John McGarrett asks to talk to his son and when Victor puts the phone up to him, he tells Steve, “Listen to me, Champ” and admits that he lied to him. He further states that he loves him and then tells Steve to do the right thing.
Victor hangs up the phone and Anton looks at Steve as the first transport is blown up by a helicopter. Victor was actually using the call to track the transport by tacking Steve’s cell phone. The helicopter shoots at the second armed vehicle and then several armed men rappel from the helicopter. Steve and the other men hold off them and Anton uses the opportunity to duck away from Steve. Steve chases him and Anton reaches for a gun, pointing it towards Steve, who shoots him. Victor calls Steve and asks what’s happening.
Upon realizing that Anton is dead, Victor responds by shooting John dead in revenge, causing Steve to shout, “No!” in horror.
Steve lands in Honolulu on an Air Force transport to attend his father’s funeral. As he is landing, a call comes in to the flight crew for Steve, and it is the Governor. He meets Governor Pat Jameson at Pearl Harbor. She wants him to come back to the island and run a newly formed task force for her.
She explains that she will give him the authority and her full backing to do what is necessary to keep her island safe. Steve is not impressed and notes that she had this meeting at Pearl Harbor, where his grandfather was killed. He thinks that she is running for re-election and turns her down. She reminds him that she knew his father and wants Victor to pay for his crimes. Steve explains that Victor already had an exit strategy and is laying low until he leaves. She gives him her card telling him to think about it.
After meeting the lead investigator, Steve changes his mind and contacts Jameson, informing her that he’ll take the job and once he’s taken an oath, gains access to the entire investigation, informing Danny that the crime scene now belongs to Steve.
Despite bad blood brewing between the two of them which eventually culminates in Danny punching Steve after Steve had Danny in an armlock, Steve adds Danny to the team, making him Steve’s partner and also the second-in-command of the unnamed Task Force.
Steve’s old friend, Detective Lieutenant Chin Ho Kelly and Chin’s cousin, Kono Kalakaua soon join the force with the group later deciding to name themselves Hawaii Five-0.
As a result of joining the Hawaii Five-0 Task Force, Steve also joins the Reserves which means that while he can aid and participate in active investigations that the team usually handle, there’s also the chance that Steve can be recalled to active duty or given orders to go on a new albeit classified mission for the Navy.