During World War II, tug boats conduct what are called salvage missions - picking up disabled ships. Not well equipped with weaponry, the tugs are sitting ducks for enemy fire. As such, the crew working the tugs have precarious lives, many with deep seated emotional problems. Before the Americans join the war, ex-American military man David Ross is assigned to captain a tug for the British military. He is shown the ropes by an old friend, Captain Chris Ford. Chris currently shares a flat with a young beautiful Italian-Swiss woman named Stella, who came with the flat and who lives a reclusive life there. Chris is the latest in a long line of tug boat captains who have lived there, each who has found another person to take over the flat and the associated looking after of Stella if anything is to happen to him. That person is given a key to the flat, the key only to be used if needed. The first in the series was Phillip Westerby, to who Stella was to be married before Phillip was killed.