Henry Sanford, contracted to build a lighthouse at Keyport, is attracted to Kate, the wife of wealthy Morgan Leroy, who becomes jealous of Henry. Meanwhile, Bill Lacey, one of the crew of elderly master diver Caleb West, covets Caleb's pretty young wife Betty. One day, Bill is injured in an accident at the lighthouse site and taken to Caleb's home, where Betty nurses him. Meanwhile, Kate has quarrelled with her husband about Henry. Bill persuades Betty to leave with him for Portland, but she regrets this and returns, realizing she loves Caleb, although he refuses to take her back. In a shipwreck involving Bill, Caleb dives to retrieve his body. Captain Bell tells Caleb that Betty had worked the air pumps, ensuring Caleb's life. He realizes that she loves him and is reconciled with her. The other couple, Morgan and his wife Kate, also come to an understanding.