Young flatmates Chrissy and Jo find a stranger, student Chef Robin Tripp, asleep in their bath the morning after the farewell party for their departed flatmate Eleanor. They are taken by Robin, and are especially impressed by his culinary skills at breakfast. Neither Chrissy or Jo can cook, and "Eleanor didn't leave the recipe for toast."
Chrissy and Jo are both from regional England and moved out on their own to live in London. They both work for the same firm. When he meets the girls Robin has been in London two days, having moved from his home town of Southampton to attend college.
The girls are unimpressed with Gabby (Helen Fraser), a pushy young woman who arrives hoping to move in to Eleanor's room. Learning that Robin has been staying at the YMCA they easily convince him to move in.
Robin moves in on a platonic basis, and Chrissy tells the Landlord, George Roper that Robin is gay to pre-empt objections to the mixed-sex living arrangement. In the second episode Robin's true sexuality becomes known to Mildred. Mildred openly flirts with Robin at every opportunity.
Robin frequently acts in a flirtatious manner toward Chrissy and Jo. The women have no romantic interest and spurn his mild advances, and quickly adapt to his presence in the flat.
Landlord George Roper, in truth a sub-letting landlord placed by the council, is a bumbling, accident-prone and gullible man under the thumb of his domineering and sexually-frustrated wife Mildred. Mildred takes out her frustrations with George's lack of class and sexual inadequacy by making suggestive remarks to Robin and frequently siding with the tenants against George. Yet for all their battles the Ropers are a devoted couple.
Robin's friend Larry, a lovable rogue, appears in two first season episodes. In the second season he moves into the loft apartment and is a frequent source of trouble. Another occasional cast member is George's friend, dim schemer Jerry.
Robin's brother Norman Tripp (Norman Eshley) appears through the final season, and starts a romance with Chrissy. Norman Eshley had a previous guest role in the series two years earlier playing a different character, and was also a member of the main cast of the spin-off series, George and Mildred in which he played The Ropers' snobbish neighbour Jeffrey Fourmile.