A Naval instructional film: an old salt (a Gunnery Petty Officer) 'conjures up' a conducted tour of a representative cruiser, HMS London in Scapa Flow, for a young man about to enter the Navy.
The deck fittings, armament, bridge and other superstructure (of HMS London after refit) are studied from bow to stern, with the 'tour' interrupted by film illustrating the working of equipment: an anti-aircraft action, the launching and recovery of a Walrus reconnaissance plane, the firing of torpedoes etc. Brief explanations of the physical structure of the ship and of the electrical systems on which its 'life' depends are introduced into a below decks tour which shows a lower steering position and the engine room, and gives a cursory impression of crew's quarters etc. Besides basic knowledge of ship's equipment, the film also seeks to convey a few more abstract lessons on naval vocabulary, customs (role of Marines), traditions (feature film footage of 19th Century naval battle) and emotions, particularly the sailor's feeling of attachment to 'his' ship. Summing up the complexity and potential of the modern war ship, the Petty Officer tells the youth "the rest is up to you, son".