Percy Brand is a crook, a veteran of various cons and schemes. Unfortunately, he is regularly sent to prison by judge Sir Edward Crichton. That does not bother Percy too much, but what does concern him is that his son, Colin, does not discover what his dad does for a living. Percy tells him tales about being a missionary in China when he is released in 1938, a military chaplain in North Africa in 1941, and a freed prisoner of war in 1946 to cover his absences in gaol. While Percy is "away", Colin is cared for by Aunt Florence.
When Colin grows up, he chooses to become a barrister. By coincidence, it will take him seven years to achieve his goal, the same duration as Percy's latest sentence. When Percy is freed, he arrives just after Colin is called to the bar. Colin informs him that he has secured a position as an unpaid marshal, i.e. an aide, to a judge to gain experience, and not just to any judge, but to Percy's nemesis, Edward Crichton. Percy decides to retire from his life of crime rather than risk coming into court and finding Colin there.
Retirement to a cottage on the south coast of England is not enough to keep Percy (and Florence) out of mischief. He hears about the smuggling that took place before the conscientious Police Sergeant Bolton arrived. Soon Percy is bringing in brandy from France, hidden inside sharks he "catches".
Then an old acquaintance, "Major Proudfoot", comes to see him. Proudfoot has planted a story that an explorer was murdered and robbed of 100,000 quid of emeralds he found in Brazil. Now he has a buyer lined up for the non-existent jewels, which he wants Percy to pretend to smuggle in. Percy has a better idea, involving fake policemen and himself as a customs officer, but the plan goes awry when Judge Crichton arrives to meet his wife, returning from a trip abroad. Percy manages to steal a launch, but is eventually caught. To compound his misfortune, he is to be tried by Crichton, a last-minute substitute for a judge afflicted with gout.
Florence comes up with the idea to add a fake case to the docket to occupy Crichton's remaining time on that particular circuit court, with the assistance of Percy's friends and associates. Mary Cooper brings her publican husband into court over a slander repeatedly uttered by their pet parrot. However, the judge becomes fed up with the case and finally dismisses it, leaving Percy's trial for the next day. The gang then try to frame Crichton for smuggling, planting contraband in the car they arrange for the judge and Colin to take that night and then making an anonymous call to tip off the customs agents. Crichton decides to take a walk first, and he and Colin get lost. They inadvertently trigger a burglar alarm when they reach a house and are taken at gunpoint to the police station.
Colin later "confesses" in order to try to straighten things out, but is not in time to prevent the judge and Percy from being driven in the same van to the assizes. Along the way, Percy confesses everything to Crichton, who is amused. He sends Colin on an errand. Thus when Percy is brought into the courtroom, Colin is absent. The judge then recuses himself, as he has had social contact with the defendant, leaving Colin none the wiser. Out on bail, Percy bids farewell to Colin, telling him that he has come out of retirement for one more trip.
A. H. Weiler wrote in The New York Times: "Robert Morley contributes an outstanding performance as the stern judge who finds himself as much outside the law as within it. Although he never cracks a smile, chances are he will force a few on the customers. As a matter of fact, they should find most of the cheerful disorders in Law and Disorder irreverently funny and diverting". The TV Guide review stated it had "a tight screenplay, with not a word wasted, and sharp acting by some of England's best characters. This is a good example of the 1950s Brit-Coms and there is so much joy in watching Morley acting with Redgrave that it seems a shame a series of films weren't made with these two characters pitted against each other."