When Ms. O gets sprayed by a plant and starts turning weird, Dr. O sends Olive and Otto on a mission to find the cure. The only thing that can bring Ms. O's old partner O'Donahue out of retirement is the one thing that put him there in the first place: a mysterious villain and a case that's gone unsolved for years.
Dr. O takes the lead on the case of a strange medical crisis that causes chaos right in middle of Odd Squad HQ. Olive, Otto and Oscar help Ms. O host a lunch for some very important but easily offended guests.
When the alarm system at Headquarters is triggered, Olive, Otto, Ms. O and Oscar must avoid a series of booby traps in order to shut it off. Olive and Otto explain to Ms. O how a case went wrong, each in their own way.
When the members of Soundcheck go missing, Olive and Otto must bring them back together in time for their big concert. When all of Odd Squad comes down with a case of the jinx, it's up to Oscar and Dr. O to save the day.
A villain uses one of Oscar's gadgets to cause destruction around town, which eventually leads to Olive getting kicked off the squad. Olive and Otto are called in to help when Polly Graph mysteriously quits lemonade stand.
In the middle of summer, Olive and Otto must figure out why parts of the town are turning snowy and cold. Olive and Otto interrogate two suspects to figure out which one is innocent and which one is guilty.