When a woman is found dead with a bottle of pills that are lab trial samples, Lassiter and Gus, who are taking the same tap class, team up to dance their way to catching a murderer.
A car is pulled out of the river with a dead woman inside. Lassiter and Juliet are investigating the crime scene. Shortly after, Shawn and Gus arrive on the scene. Shawn looks more closely in the car and determines that the dead woman wasn't in the car alone, and therefore hypothesizes that she was murdered.
Gus tells Shawn he has to get to tap class. Lassiter overhears and inquires about it. At the tap class, Gus is surprised to see Lassiter show up. Lassiter insists Gus let him take the class with him as a means to follow through on his therapist's orders to try something new.
Gus is hesitant, but helps Lassie get in the class – which is clearly more advanced than Lassie's current skill level. Lassiter is a terrible tapper, and in turn, embarrasses Gus who had pulled strings to get Lassie a spot in the class. The class ends and Lassie is about to give up on tap all together, but Gus teaches him a few moves. While they are shuffling their feet, they start to talk about the murder case they saw earlier. Lassiter discovers that tapping eases his stress and that he can concentrate on the case more. Lassiter says that he found a bottle of unmarked pills that he sent to lab to have checked out. Lassie explains the pills to Gus and Gus right away says the pills he is referring to are trial sample pills. Lassiter thanks Gus for the help and asks him to tag along on his investigation, as Gus has proven himself useful. Shawn shows up and is immediately jealous that Gus is working with Lassiter on the case and not him. But this gives Shawn a challenge. He bets he can solve the case before Lassie and Gus can. Gus is game, since Lassie gives Gus more respect as a partner than Shawn ever has.
Gus determines that the pills were in fact trial hormone pills, a fertility drug that is experimental, and that the test subject would have had access to them. At the lab the pills came from, Lassiter and Gus question Lillian, the lab tech that was on the job during the time Desiree obtained the pills. But she denies any foul play; she was the only lab tech there. She admits that Desiree was the girlfriend of a lab tech she works with named Ben. Lilian admits that it was she who gave Ben the pills to give to his girlfriend. But Gus figures it out that there must have been a second lab tech Lillian didn't know about because it was a "double blind" clinical trial. After Lillian leaves the room, Shawn shows himself, dressed as a lab tech. He had overheard everything Gus said, and now knows their lead – Ben.
Shawn gets word from Henry that he and Juliet will be working on the case that Lassie and Gus are on – only they will conduct separate investigations. Now the race is on to find Ben. The two teams, Lassie and Gus, and Shawn and Jules both show up at the lead's home at the same time.