Synopsis - Prelude to Murder a/k/a Dressed to Kill Opening scene is Dartmoor Prison where a prisoner is making music boxes, another prisoner approaches him making a proposition to tell what he knows, distrusting the fellow, a comment is made where the man will take his chances, having less than two and a half years before his release. There is no telling who might be on the inside working for Scotland Yard.Auctioneer is introducing the Dartmoor music boxes to his potential buyers, one such box is purchased by Dr. Watson's friend Stinky, another identical box is bought by a young lady, the third and last box was obtained off-camera by a gentleman. A well-dressed man, Colonel Cavanaugh, taps on the closed door of the auction house, requesting the buyers' names of the sold music boxes, saying for sentimental reasons and five pounds. The man is given the information he requested, he leaves, gets into his chauffer driven vehicle, mentioning word was received late about the boxes becoming available for sale. Dartmoor was late getting the information to the accomplices.Julian Emery known as Stinky stops by to see Dr. Watson, friends since school, a noticeable bandage on his forehead prompts a burglary conversation with Holmes explaining his wound. Holmes and Watson go to see the musical box collection finding the box he purchased earlier is at his house, the burglar took one just like it. Stinky plays the box tune, where Holmes picks up on the notes, whistling the melody. Holmes and Watson leave, Stinky receives a call from Mrs. Hilda Courtney, inviting herself to his place tonight. She arrives, Stinky is smitten by her beauty as she examines the inexpensive box, her chauffeur throws a knife killing him. She admonishes him for entering, killing Julian, and tells him to get out. They both leave with the box in her possession. The chauffeur is named Hamid, working with the Colonel and Mrs. Courtney. The three of them are in the same vehicle as they drive off, Hilda telling the Colonel of the murder. Mrs. Courtney first was made aware of Sherlock Holmes' involvement of a stolen music box due to the relationship with friends Stinky and Watson.Holmes and Watson visit the murder scene, greeting Inspector Hopkins, learning time of death from Detective Sergeant Thompson, and suggesting to Dr. Watson a visit to Ebenezer Crabtree, auction house proprietor. They learn the Colonel inquired the purchaser names and Holmes suggests they visit the other man buying an identical music box, a Mr. Kilgour. Stopping by the Kilgour residence, they meet by the alleged housekeeper, inviting themselves inside, proposing to wait for the Kilgour's. The housekeeper hires a cab going to a better part of town, questioned by the cab driver about her attire, they depart, later revealed to be Hilda in disguise. Holmes discovers the Kilgour child bound in a closet, frees her, realizing the housekeeper was not the Kilgour charwoman but an imposter, stealing the music box from the child. Holmes is off to see the woman that bought the third music box.The Colonel and Hilda drop in on the woman running the toy shop. The music box was earlier purchased by Holmes, his card left with the proprietor, just in case anyone should inquire about the box. The three criminals are now being followed by Detective Thompson in a cab. The three are not fond of Holmes on the case, the hunters are being hunted.Holmes and Watson at the commissioner's office learn Thompson is following the three culprits, they also learn John Davidson is the convict's name, serving a seven year term for stealing the Bank of England plates. Davidson was an engraver for the Bank, he managed to steal, quickly hide the five pound note plates before he was caught, charged with a lesser crime. Davidson felt he needed to inform his confederates of the plates' location for fear of someone discovering the location prematurely. They learn Thompson has been run over by a cab, not an accident, but murder according to Holmes, more reason to find the three criminals.Holmes deduces the tune of the boxes is the clue to the location of the plates, but exactly how to extract that information he thinks he will get closer learning more about the tune itself. He goes to an actor's pub where he finds Joe Cisto, to help him identify the song. Joe helps, now Holmes must decipher the variations of the song from the three boxes, one of which he has.Returning home with Watson they see their home has been ransacked; the burglars were looking for the box which Holmes hid in the biscuit jar. Watson gives Holmes the clue he needed to deciphering the code, numbering or lettering the keys. Dr. S are the key words left to be resolved, the rest are known to Holmes.Holmes is at the tobacconist to identify the special blend of tobacco and its buyer. He goes to Mrs. Courtney's house, identifies the time they met at the Kilgour's. She denies knowing. He identifies the tobacco is hers, she admits she set the trap to lure him to his demise. Hamid and the Colonel escort Holmes to a garage, hanging him on the upper beam while running a motor emitting a deadly gas. The two murderers leave Holmes hanging but he is able to shimmy his way off the beams, escaping to safety.Watson is visited by Hilda Courtney on the rouse she is looking for Holmes's help, while she distracts Watson with a smoke bomb, she steals the box Watson inadvertently shows her by moving the biscuit jar before he went for the fire extinguisher. Watson is tending to Holmes' injured wrist from the garage beam, where he quotes Dr. Samuel Johnson. Holmes now knows where the plates are located, on the third shelf in the Secretary of Dr. Johnson's library of his museum home.A tour of The Samuel Johnson House is giving by a museum employee as the three criminals key open the Secretary, Dr. Johnson's bookshelf, finding the plates, the three rejoice, but Holmes points his pistol at them. Hamad throws his knife at Holmes, misses Holmes and Holmes shoots him. Hamid goes down wounded, Watson shouts out "Holmes" at the sound of the shot and runs upstairs with Scotland Yard. All crooks are arrested, the plates are turned over to the Inspector Hopkins.