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Basil, the rodent Sherlock Holmes, investigates the kidnapping of a toy maker and uncovers its link to his archenemy, Professor Ratigan.

In Victorian London, England, a little mouse girl's toymaker father is abducted by a peglegged bat. She enlists the aid of Basil of Baker Street, the rodent world's answer to Sherlock Holmes. The case expands as Basil uncovers the crime's link to a plot against the Crown itself.—Kenneth Chisholm <kchishol@execulink.com>

Set in 1897 London, England. Basil is a skilled detective who has been trying to stop his arch-foe, Professor Padraic Ratigan for years. Every time Basil tries to stop Ratigan or when he tries to find a clue on his whereabouts, Basil gets outsmarted by the mobster and his clues become a dead end for him. When a young female mouse named Olivia informs Basil about her father's abduction, the detective becomes determined to bring Ratigan to justice. Basil soon gets help from Dr. David Q. Dawson and Toby, a smart yet resourceful dog owned by Sherlock Holmes, in order to stop Ratigan once and for all, who plans on overthrowing the mouse queen during her annual jubilee.—dawsonpersi

The clues are in, the chase is on, and the case of the century is about to break wide open in Disney's greatest little mystery in history. Let the creators of Aladdin and The Little Mermaid take you on an adventuresome journey through the cobblestone streets of 1897 London, where some suspicious "mousechief" is the suspenseful start to this thrilling musical adventure. Olivia, the brave daughter of a beloved London toymaker, turns to Basil of Baker Street for help with her father's disappearance. Basil's jolly assistant, Dr. Dawson, and loyal dog Toby lend a hand ... and nose ... as they sniff out clues through their charming miniature world. The final chase leads to Professor Ratigan (voiced by Vincent Price), a hard-hearted criminal whom Basil must outwit to save all of Mousedom.—Disney

In 1897 London, a young mouse named Olivia Flaversham (Susanne Pollatschek) celebrates her birthday with her single father, toy-maker Mr. Flaversham (Alan Young). However, a bat with a crippled wing and a peg leg arrives unexpectedly and kidnaps Flaversham. Flaversham is a master of creating mechanical toys that look very life-like.

Olivia leaves to find Basil (Barrie Ingham) of Baker Street, the famous Great Mouse Detective, but gets lost. David Q. Dawson (Val Bettin), a retired army surgeon mouse previously of the Queen's 66th Regiment newly returned from Afghanistan, meets Olivia (while she was sobbing alone in the rain) and agrees to escort her to Basil's residence. They manage to find his rooms at 221 1/2 Baker Street.

Basil is a bundle of energy, running around the flat, ignoring his two visitors, in anticipation of bringing his latest case to a successful conclusion with an experiment in ballistics. Alas, the experiment is a failure, and the detective is thrown into a deep depression, still unwilling to help poor Olivia. Basil is an expert at disguises and is shown to have remarkable powers of deduction as he surmises that Dawson was a surgeon in the military and returned recently from Afghanistan. Mrs Judson (Diana Chesney) is Basil's housekeeper.

Being busy already, Basil initially dismisses them. Olivia then mentions the bat that abducted her father, and Basil realizes that Olivia saw Fidget (Candy Candido), the assistant of Professor Ratigan (Vincent Price), the criminal mastermind whom Basil was working to catch. Ratigan is the worst criminal in London, a veritable Napoleon of Crime.

It is then revealed that Ratigan kidnapped Flaversham to create a clockwork robot replica of the Queen of the Mice (Eve Brenner), so that Ratigan can usurp her place as "Supreme Ruler of all Mousedom". Flaversham initially refuses to participate in the scheme but capitulates when Ratigan threatens to harm Olivia. Ratigan gives a list of materials to Fidget to arrange, and which also had Olivia listed, meaning that Ratigan wanted Fidget to kidnap her. One of Ratigan's henchmen calls him a rat, which he hates. Ratigan unleashes his pet cat Felicia on the henchman to devour him.

Meanwhile, Fidget appears in Basil's window, then suddenly disappears. Instantly, Basil is after the villain, with Dawson reluctantly in tow, but all they find are peg-legged footprints and the bat's cap. For a detective of Basil's caliber, these clues are more than enough, and he is off to find the kidnapped Flaversham. Basil wheedles Dr. Dawson into enlisting as his assistant, and little Olivia tags along, too, much to Basil's disgust.

Basil, Dawson and Olivia take Toby, Sherlock Holmes' pet Basset Hound, to trail Fidget's scent. They trace Fidget to a human-sized toy-shop. Basil skulks about in search of Fidget and finds some puzzling clues: toy soldiers without their uniforms and wind-up toys with all the gears missing.

Fidget ambushes and kidnaps Olivia before Basil and Dawson can stop him. While searching the area, Dawson finds Fidget's checklist given to him by Ratigan. Basil does some chemical tests to the checklist, finding traces of brandy, coal and seawater, which lead him to deduce that the note came from the "Rat Trap", a tavern near the junction of the sewer and the Thames.

Meanwhile, Ratigan uses Olivia to threaten Flaversham to complete the creation of the robot Queen.

Basil is also a master of disguise, and he swiftly outfits himself and the protesting doctor as sailors. Together they infiltrate the Rat Trap, a disreputable pub filled with low-life ruffians, just the place to search for one of Ratigan's minions. They spot Fidget there, and follow him to Ratigan's headquarters, only to be ambushed by Ratigan and his henchmen. Basil realizes that he has walked right into a trap and is crestfallen as Ratigan asserts that the superior mind has triumphed. Ratigan has the pair tied to a spring-loaded mousetrap connected to a Rube Goldberg machine of various killing devices.

Basil and Dawson tied to a mousetrap which will snap when a metal ball drops onto the trigger. Not content with this, Ratigan has set the snap of the mousetrap to fire a gun and a crossbow at the unlucky pair, which will in turn cause an ax to chop them to bits, which will bring an anvil down on whatever is left of the great mouse detective, with a rigged camera to record the results. The entire trap is set in motion when a record of Ratigan's song plays to the end, pulling a string that releases the fatal ball.

Ratigan then sets out for Buckingham Palace, where his henchmen hijack the royal guards' roles and kidnap the Mouse Queen. The Queen has ruled the Kingdom for 16 years and this day is when she is throwing a grand party to celebrate her diamond jubilee.

Mortified at being outwitted, Basil is once more plunged into depression and puts up no resistance, not so much as attempting to think of a way out of the trap. Dawson snaps if Basil has given up, then they are might as well set the death trap off now and get it over with. At that last remark, Basil realizes to his delight the way to escape: setting off the trap now.

Their only chance is for Basil and Dawson to snap the mousetrap themselves at just the right moment. The trap clamps down on the metal ball, thus protecting the pair from being caught in its powerful jaws. Moreover, the pressure pops off the mousetrap's hinge, which knocks the gun aside, which shoots the crossbow, which deflects the arrow, which shoots the ax, which comes down between Basil and Dawson, which cuts them free just in time to avoid being splatted by the anvil. In the shock-wave of the impact, Olivia is jarred out of the battle she is trapped in and caught by Basil who also grabs Dawson for the photo now marking the detective's triumphant thwarting of the deathtrap.

At Buckingham Palace, Ratigan forces Flaversham to operate the toy Queen, while the real one is taken to be fed to Felicia, Ratigan's pet cat. The toy Queen declares Ratigan the ruler of all Mousedom, and he announces his dictatorial plans for his new "subjects".

After Basil, Dawson, and Olivia save Flaversham and the real Queen, they restrain Fidget and Ratigan's other henchmen, while Toby chases Felicia until she jumps over a wall, inadvertently into a pack of Royal Guard Dogs. Basil seizes control of the mechanical queen, making it denounce Ratigan as a fraud while breaking it into pieces. Realizing Ratigan's treason, the enraged crowd attacks, but Ratigan escapes on his dirigible with Fidget, holding Olivia hostage.

Basil, Dawson, and Flaversham create an airship from a matchbox, balloons, and a Union Jack, and set off in pursuit. Ratigan tosses Fidget overboard to lighten the load. However, Basil jumps onto the dirigible to confront Ratigan, causing it to crash straight into Big Ben's clock-face. Inside the clock-tower, Basil restrains Ratigan, rescues Olivia, and safely delivers her to Flaversham. Ratigan breaks free and attacks Basil. Ratigan's rage at being thwarted once again causes him to snap. He rips his clothes to shreds and stands revealed as a fierce and deadly rat!

Ratigan tackles Basil and the two go tumbling down to land on the hands of the great clock. The detective is battered mercilessly until he finds himself hanging by his fingernails on the edge of oblivion. However, when the clock strikes 10:00, the vibrations cause Ratigan to fall to his death. He attempts to take Basil with him, but Basil grabs a part of Ratigan's dirigible and saves himself.

Back at Baker Street, the group recounts their adventures. The Flavershams depart for home, and Dawson reluctantly resolves to leave as well. A new client arrives, and Basil introduces Dawson to her as his friend and investigative partner, prompting Dawson to remain and assist in Basil's future cases.