Plot summary
Scorpion works with the World Health Organization to stop the dangerous Marari virus from spreading throughout South America and causing a pandemic. They travel to the Amazon rainforest to locate an endangered monkey species called the Homboldt Capuchin that may have the antibody for the cure. Meanwhile, in order for their marriage to work, Happy wants to express herself better, so she drags Toby to see "quack" therapist Dr. Cecil Rizzuto ( Penn Jillette ) for premarital counseling. Later, Walter identifies with Cabe's emotional pain from losing Allie after his own heartbreak over Paige and actually shows some empathy towards him.
Credits
Adapted from Wikipedia contributors, List of Scorpion episodes. HTML formatting and reference markers removed.