"Five-Sided Triangle", while geometrically incorrect, might be a better title for this film than the two it has. Arthur Crisp, a private in the Queen's Guards is forced to leave his ex-fiancée Christine in the empty house of a high-ranking civil servant whose son Miles discovers her there and promptly falls in love. His sister Alex decides that it would be best if Christine got together with Arthur, not realizing that he's worshipped her from afar. A further complication is that Arthur's commanding officer is in love with Alex.