At a quaint sidewalk caf¿, Serge Cluvarias and his young date Ariana sit enjoying a late dinner. Their quiet evening is suddenly interrupted when a mysterious masked figure dressed as a ninja leaps down into the caf¿ from the rooftops above, and, without warning, shoots Serge dead. The ninja then makes a quick escape by leaping onto the restaurant awning, performing an amazing in-air somersault, and diving into the street to run away.
When the police arrive at the scene with Monk in tow, it only takes the obsessive compulsive detective a moment to tie together a handful of clues. Sugar cubes missing from the tables, sawdust on the ground, a somersaulting ninja, and an elephant gun... is there a circus in town?
The investigation shifts to the Dratch and Denby Traveling Circus. Serge, the dead man in the caf¿, was the circus' ringmaster, while his young date was the circus' horse trainer. As Monk questions Ariana, he learns that she suspects Serge's jealous ex-wife - Natasia Lovara, "The Queen of the Air" - of the murder. Natasia is a skilled acrobat, and certainly more than capable of pulling off the high-flying feats displayed by Serge's killer. But when Monk and Sharona go to speak with her, they come face to face with Natasia's alibi: a broken leg suffered after a fall during a routine two weeks ago. With her leg in a cast, there is no way Natasia could be responsible for last night's murder... or is there?
As he continues to follow the clues to Serge's murder, Monk makes another startling discovery: Sharona, his fearless assistant, may not be as fearless as she seems. As it turns out, she does have one phobia: a deadly fear of elephants. When Monk dismisses Sharona's fear as silly, she becomes enraged by his insensitivity and nearly quits.
Still angry with one another, the duo continues to pursue Serge's killer. Convinced that Natasia is somehow involved, Monk convinces the police to get an X-ray of her foot. But much to his dismay, it is indeed shattered, so it would appear that there is no way she could have been involved with Serge's murder the night before. Meanwhile, back at the circus, Natasia is approached by Heinz, the circus' elephant trainer. Heinz confides in Natasia that her "secret" is safe with him, as he would never do anything to hurt the one he loves. But Natasia, it seems, isn't held back by such petty matters of the heart.
Monk decides to attempt to patch things up with Sharona by helping her overcome her fear of elephants. He brings her to meet Heinz's elephant Dede - but both are horrified by what happens next. Heinz practices an age-old routine with Dede, where he places a watermelon under her foot, gives a command, and the mammoth elephant gently places her foot on the melon without crushing it. But then, with another command from Heinz, Dede brings her foot down hard, smashing the melon into pieces. In the next part of the trick, Heinz fearlessly places his head under Dede's foot, again gives the first command, and the elephant gently places her foot on Heinz's head. But, unbeknownst to Heinz, there is a walkie talkie hidden near the elephant's ear, and on the other end of the walkie talkie is Natasia. She gives the second command, and Dede brings her foot down on Heinz's head, killing him instantly and sending Sharona's fear of elephants into overdrive.
As he does his best to comfort a distraught Sharona, the pieces of the puzzle finally fall into place for Monk. How was Natasia able to kill Serge and then make an acrobatic escape with a broken foot? It was easy... with a bit of elephant-sized help. Monk determines that Natasia's foot was not broken at the time of the murder - she faked the fall two weeks ago in order to fool everyone into thinking her foot was broken. Then, after killing Serge and making her escape, she used Dede and the "crush" command to break her foot for real, thus giving her the perfect alibi.
Another unlikely crime, solved by San Francisco's most unlikely detective, Adrian Monk.