Navy Instructional film on the importance of machinery space watchkeeping. The film follows five junior Marine Engineering ratings, each in a different ship, as they make rounds on various pieces of equipment, such as diesel generators, pumps, oil and fuel tanks and the ship's steering gear. The voice-over takes the form of a humourous competition between a Chief Petty Officer, in favour of doing the job properly, and a smooth-talking mystery voice, encouraging the ratings to relax and not check everything as they should. The results of proper checking, or failure to do so, are shown, re-emphasising that the proper inspection of machinery is important for the safety and efficiency of the ship. The Leander Class frigate HMS Sirius (F.40) and the Daring Class destroyer HMS Decoy (D.106) make brief appearances.