A Maritime Board of Inquiry investigates the loss of the merchant ship, the Black Rover . Its captain, Jim Parker, offers the following testimony on his own behalf: Jim is recommended by Fred Winthrop to his father, owner of the Winthrop Shipping Line, to command the Black Rover after its captain and crew refuse to make the voyage. Jim, who has just received his captain's papers, agrees, unaware that Winthrop is illegally running a cargo of contraband weapons. Fred becomes the ship's first mate and selects a crew of a mostly criminal element not likely to investigate the ship's cargo or submit to Jim's authority. Jim is also unaware that his fiance Helen has disguised herself as a galley boy and sneaked aboard with the assistance of Gimpy, the cook. As the ship sets sail for Santino, by way of Sea Turtle Island, Jim becomes uneasy about his sullen crew. Jim quickly sees through Helen's disguise and orders her to disembark at the next port, but she sneaks back on-board by hiding in a cargo bundle and remaining in the cargo hold. Once at sea, Jim realizes Fred's fear of inspecting the cargo and discovers the guns. When Jim orders the Black Rover to turn around, Fred incites the crew to rebel, and in the ensuing melee, the captain is knocked out. Fred then has Jim bound and assumes command of the ship. When a powerful storm arises, the crew begins to drink and carouse, frightening Helen, who leaves the hold and pleads with Fred to free Jim. Instead, Fred and several drunken sailors attack Helen. Hearing her cries, Jim breaks free and helps her onto the stormy deck before being knocked unconscious by Fred. When Jim awakens, he has no memory of his identity and finds the ship abandoned. After being washed overboard, he ends up on an island where he is befriended by an old sailor named Peg, with whom he haunts a local bar, passing the days drinking. With a small cachet of hoarded pearls, Jim and Peg plan to purchase a boat to leave the island. One day, at the El Marino Café, Jim drinks with some of the Black Rover sailors, unaware of their identity. Fred, who is also in the bar, attempts to sell the remainder of the ship's cargo. When Peg flashes the money from the the sale of the pearls, he is eyed by several suspicious looking men in the bar and a fight quickly breaks out. In the struggle, Fred is shot and Jim struck on the head, which restores his memory. Back at the court of inquiry, Jim explains that the only corroboration he has is Helen's presence. The court has already interviewed Helen and indicate that her account is of little value as she, like Jim, has no idea where they were shipwrecked. The inquiry is interrupted when Winthrop asks to be heard and confesses to the plot and takes blame for the loss of the ship, crew and his son. Seeking retribution, he offers Fred control of the entire Winthrop Line.