The team searches for a pair of limited edition sneakers after they are stolen from a foreign ambassador.

Feeling guilty over the stabbing, Charlie puts his attention on finding a serial killer using math theories to help the team solve the case before another life is taken.

Don and his team are called in to investigate who is behind a deadly gambling ring that is running a high-stakes Russian roulette tournament. Also, Don and Charlie become concerned about Alan's financial health.

After Charlie and Amita get married and begin preparations for their London adventure, they put a slight hold on their wedded bliss when they assist the team in helping Don track down the whereabouts of his gun after it goes missing.