The restless nature of sailor Tom Mansey pushes him to trade his work on a Thames dredger for a place on a coal cargo ship running the continental coast. A born boxer with the power to charm when he wishes, Tom”s colorful family is left to its own devices when he”s away: brother Leonard builds his life around the redemption of the Salvation Army and his kid sister Violet–who without exception is known as Vi-lert–is a serious contender to become an Olympics-caliber swimmer. Also left on shore is ex-girlfriend Daisy, who Tom has forcibly reunited with another paternal candidate so he could slip the knot himself, and Nancy, a meek girl who has fallen harder for the sailor than she would like. Tom”s plans to pursue Nancy further are complicated when he is abandoned on the island of Madeira–with no tears shed by the bruisers on the ship”s crew–and encouraged by the local bar owner to marry his daughter. Though he is fond of the kind and lovely Lucia, it”s not part of Tom”s plan, and he works as a mountain sled runner for the tourists until he can catch a ship and leave the impoverished island.
When he finally returns to London (by sneaking aboard a docked grain ship and throwing a sailor overboard once they”re at sea, thus creating an open position), Tom finds that Leonard”s antipathy towards him has grown. The feeling is mutual. Sister Vi-lert”s constant training has strengthened her considerable swimming skills, but it has also nurtured a frustrating boredom felt by the adventure-seeking girl. Nancy wishes Tom would stop looking to the sea and offer to settle down on land, for she won”t consider a relationship with him otherwise. But Tom chooses the “Mary Meadows,” a ship making its way to the Grand Canary islands and beyond.
This time, however, another stowaway is on board: Vi-lert hides herself in the hold, lonely for her oft-absent brother and tired of the city. Along the voyage the crew mutinies, believing the owners are planning to sink the ship and its worthless cargo for the insurance money. They strand the well-meaning captain and Vi-lert at the port of Santa Catalina and go off to search for sunken treasure, keeping one of the owners and his diving equipment on board for that purpose. It falls to Tom and a trustworthy mate to form a plan that will overthrow the mutineers and allow him to rescue Vi-lert from the island of Las Palomas, and then navigate their way back to London.