Karen Andersen, a flight attendant, meets and falls for Major Frank Kelly, a U.S. Army Intelligence Officer on a flight from Manila to Honolulu in early December 1941. Frank believes a high-ranking officer of Admiral Yamamotos' staff, named Shigata, is aboard the flight as well. “Why?” he wonders. They have dinner and afterward run into Shigata, whom they follow to a house on Keeaumoku Street. Later when Frank fails to pick up Karen, she goes to the house looking for him. Shigata sees her and believes she has discovered his Fifth Column Organization and has her kidnaped. While investigating her disappearance, Frank discovers Shigata tracking the ships in and out of Pearl Harbor. Shigata is injured during the arrest and held captive in the hospital. He dies mysteriously before they can question him. Karen escapes her captors as the attack starts. The attack is over, but the death of Shigata must be investigated.