At around 00:00 on 18 September, the port lights suffered an unexplained malfunction. Seizing the opportunity, Lieutenant Grudziński prepared the submarine for departure. The crew was forced to delay by the arrival of an Estonian officer. After a 30-minute inspection, he deemed nothing to be out of the ordinary and bid the Poles goodnight. The crew resumed with their plans. Two Estonian guards at the dock were lured aboard and nonviolently taken prisoner, the lighting in the port was sabotaged and the mooring lines were cut with an axe. Both engines were started, and the submarine made her escape in the darkness.