The Wreck of the Mary Deare (1959)

In the English Channel John Sands, captain of a small rescue ship, finds the freighter Mary Deare drifting. Although there's only a little fire, the whole crew seems to have left the ship. John's already looking forward to a large salvage fee, but then he finds first officer Gerald Patch still on board, who sends him away. Although he doesn't understand yet what happened on the Mary Deere, Sands allows Patch to persuade him not to talk about what he saw on board and to drag out the official investigation of the incident.