Plot summary
Shawn talks with Detective Lassiter at a bar, and gets details on the potential homicide of an astronomer. Lassiter is depressed about the fact that he has not been able to solve a crime in a while, so Shawn decided to solve the case, but credit Lassiter with everything. Shawn gets a job at the observatory where the man worked, and surprises Gus, who visits the building frequently. Shawn breaks into the astronomy lab, looks through the log books, and discovers a missing page. He realizes that the other astronomer likely killed his co-worker.
Shawn and Gus try to break into the man's house; while there, they notice a weird flower, and decide to take it. Gus discovers that the living astronomer is about to announce something big. They find out the flower is toxic, and Shawn realizes that this was how the man was murdered, and they catch the man.
Credits
Adapted from Wikipedia contributors, Psych season 1. HTML formatting and reference markers removed.