Gus is a closet fan of spelling bees. He knows everything there is to know, from the major players to the winning words each year. When Shawn catches him watching the Regional Spelling Bee that he Tivo'd earlier, they see that this year's favorite, Brendan Vu, collapsed while spelling a word. Shawn doesn't think it was an accident. He notices something is wrong with Brendan's inhaler. They get a call from Interim Chief Vick to come down and investigate. This is Gus' dream come true.
Vick tells them Brendan said his inhaler felt funny in his hands. When the paramedics got there, the inhaler disappeared. They need to talk to all of the suspects by 5 p.m. She wants this case solved before the Bee is over and the potential suspects scatter back to their hometowns.
Immediately Shawn eliminates all the spellers who were already knocked out of competition when Brendan went down. As he's going through the remaining suspects, word comes down that the Spellmaster, notoriously reclusive former champion Elvin Cavanaugh, has a big announcement to make. As Shawn and Gus come out to hear it, they witness Cavanaugh, up in the Spellmaster's box in the balcony, stumble and fall over the railing to his death.
Lassiter and his new partner, Juliet, think Cavanaugh probably had a heart attack or an allergic reaction. The man loved junk food and was dangerously overweight. Shawn and Gus, meanwhile, talk their way into the Spellmaster's box to investigate. When Gus' "Supersmeller" nose detects a weird odor, they suspect Cavanaugh's Chinese food may have been poisoned. They need to know for sure, so they take a few noodles with them. Now all they have to do is find a lab to do the testing.
Shawn goes to his dad for help. Henry's got a friend who runs a lab that'll solve their problem. In return, Henry wants a favor. Shawn has never finished anything in his life. Henry wants him to complete something in the form of a doghouse he started building in 1989. Shawn's desperate, so he agrees to do it. Of course, he quickly gets frustrated and quits. On his way home, Shawn gets run off the road by a van and thrown from his bike. Someone is trying to kill him!
While Shawn's at the hospital getting patched up, he and Gus check on Brendan. They notice he has a replacement inhaler. It's the identical type Jiri Prochazka, another speller, has. Only Gus informs Shawn, the doctor on Jiri's prescription does not exist. Jiri's inhaler is a fake. Shawn is now determined to finish the doghouse. He needs the results on those noodles.
Henry notices Shawn's been injured and helps him finish the doghouse. Turns out, Henry already had his friend analyze the Chinese food. It definitely was poison, a fact that Shawn takes to the cops in the form of a "vision." Unfortunately, they can't build a case off his vibes. Shawn and Gus are going to need actual proof.
Back at the Bee, Shawn poses as the new Spellmaster and he and Gus sneak back into the Spellmaster's box. There, Shawn notices distinctive indentations on the carpet. He finds a tripod in the closet with a camera attached, locked in an awkward position. The feet of the legs fit into the indentations perfectly. As Shawn moves the tripod around, he realizes Cavanaugh was spying on Jiri's father, Miklous. Cavanaugh must have suspected Miklous and Jiri of cheating and was going to disqualify the boy in his big announcement.
Back downstairs, Shawn watches Miklous as Jiri comes up to spell. He sees Miklous tapping something in his jacket and then Jiri gripping his inhaler. Shawn realizes Miklous rigged a system that sent electrical pulses to the inhaler to spell out the word for Jiri. Brendan accidentally got hold of that inhaler, and that's why it felt strange in his hands and didn't work when he needed it to. It was Miklous who poisoned Cavanaugh and ran Shawn off the road. Gus calls the police and Shawn has a grand psychic episode onstage, pointing to the inhaler as the definitive proof the cops were looking for.