Basil Rathbone and Nigel Bruce simply cruise through this lacklustre entry in the Universal Sherlock Holmes series, escorting an imperilled prince to his home country on an ocean liner. Holmes looks decidedly sniffy about the whole affair, as if lamenting the poor production values and wafer-thin sets. Watson makes the best of a mediocre job, however, at one point even bursting into song. But, then, he always did look on the bright side, which is more than the viewer can here.

After the King of Rovenia has been assassinated, Holmes and Watson are engaged to escort his son to Europe via Algiers, aboard a transatlantic ocean liner which also carries a number of suspicious persons, any of whom may be involved in a plot to also assassinate him.