She arrived at Dutch Harbor on 16 September. On 26 September, she departed Attu on her last war patrol. One day out, while en route to her operating area in the northern Kuril Islands, she was spotted and attacked by a Japanese patrol plane. Suffering no damage, she continued west. On the night of 7 October, she made radar contact with what she thought was a "small merchantman" and closed for a surface attack. Several hundred yards from the target, her deck gun fired and was answered by a salvo. The "small merchantman" in fact was the escort . An emergency dive was ordered, but the submarine failed to submerge. She then took several hits in the control room, below the waterline in the after battery room, and elsewhere.