Upon returning to Hawaii to investigate his father's murder, decorated Naval officer Steve McGarrett is recruited by the Governor to head up an elite new police task force - his rules, her backing, no red tape. Their first case involves tracking a weapons dealer connected to McGarrett's father's murder.

When an escalating gang war spills into the stands of the local high school football game, injuring several bystanders and killing a gang leader, Five-0 uncovers an unlikely partnership between Samoan gangs and a mainland mob.