Sherlock and NFL Today Host Philip Simms are arguing. Simms is the greatest knife thrower in the world, but the pay was so little that he needed a day job. Watson thinks it is a joke, so Simms demonstrates. He hits a dummy in the head and heart with a knife.
Watson asks Kitty to help her with a case. She's been following Chad Keswick, a real estate mogul, but she thinks he spotted her and wants Kitty to tail him. She declines, saying she works for Sherlock.
Harlan Emple is shirtless and solving a problem on his chalkboard. He searches an abandoned building, looking for the next clue, when he stumbles upon a dead body.
Captain Gregson and Detective Bell interrogate Emple. He was on a math hunt, Belphegors Prime. He asks for Sherlock and Joan. Gregson assigns Sherlock the case. Joan goes to leave, but he asks her to stay and assist him as Kitty is working on another assignment.
They check out the crime scene. Sherlock discovers the next clue in the puzzle hunt had been painted over. Emple gives them some names of other mathematicians who are likely playing the game. The reward is over $1.7 Million dollars.
Sherlock and Bell go to interview Byron Lowenthal. Bell knocks on his door and Sherlock hears a strange noise and pushes Bell away from the door. Someone shoots through the door. Bell searches but Lowenthal is gone.
They send the math problem Byron was working on to Sherlock's house for Harlan to solve.
Watson talks to Sherlock about Kitty. She is traumatized and needs counseling. Sherlock says he knows but she refuses assistance. Joan says Kitty needs help and Sherlock has to make sure she gets it.
Harlan solves the math riddle and has the GPS coordinates to the next clue. But Sherlock says it's not a clue, it's a murder scene. Byron has been killed. Sherlock says the treasure hunt is not a game but a trap.
Harlan is freaked out. Sherlock gets a phone call from someone who says they know who the killer is. Paul and the other contestants believe the killer is Mo Shellshocker . He runs a blog and exposes bad math. He had gotten into a nasty argument with both Ike and Byron.
Harlan is Mo Shellshocker, which is an anagram of Sherlock Holmes. As Mo, he has published some classified documents. He asks Sherlock what he did to make him unhappy. Sherlock admits that Harlan had become needy. Harlan is hurt and leaves.
Sherlock and Joan skype. Sherlock muses that the killer might be on his own treasure hunt. He knows what he needs but doesn't know who has the information. He tells Joan he is going to talk to Kitty about counseling again.
Kitty agrees without a fight. Says that Harlan/Mo actually had some interesting things on his site. Sherlock calls Paul and tells him Harlan is Mo Shellshocker.
Sherlock waits outside Harlan's home. He explains that the killer was after Mo Shellshocker for exposing a lottery card defect that less scrupulous mathematicians would exploit. The killer was Paul Ettinger who Sherlock sent to an apartment filled with police officers.
Kitty tells Watson that Sherlock won't be able to deliver on his promise to teach her everything without Watson's help. She is going to a support group meeting tonight and asks Watson to help her.