Index Case is the third episode of the 4th season of "Motive" which aired on April 5, 2016.
The victim: Chris Mancuso, an environmental consultant.
The killer: Logan Tenwick, a research scientist for Turner, a biomedical firm for which Chris had been hired to do an environmental assessment for the location of its new research facility.
Logan has been working on what he considers the definitive and groundbreaking work on eradicating breast cancer. It is through Chris' consulting work for Turner that he met who would become his girlfriend, Kierra Graff, Logan's assistant.
Chris' dead body is discovered first thing in the morning inside a sensory deprivation tank at a day spa, using such a tank which was his routine following his many business trips, the Chilean rainforest from which he just returned the night before.
This case is the first one since Oscar kicked Kennecki off of Homicide and replaced him with Detective Paula Mazur, who is an efficient yet somewhat cold loner of a person who Angie and Brian refer to as the "anti-Kennecki".
The case takes a deadly turn when Betty not only discovers that Chris died from asphyxiation by his tank being flooded with chloromine, but that he still has an active but unknown pathogen in his system, meaning the morgue being locked down. The guess is that he picked up the deadly virus in Chile.
As such, the team, who has one member hit by the virus which again could have deadly consequences for that person, has to locate the killer as quickly as possible, they suspect he/she having been infected by Chris and now being the unsuspecting carrier of the virus infecting innocent people in his/her path.
The virus also being unknown in nature adds an extra level of concern as Betty knows the CDC can only identify it if a victim comes forward who knows when he or she would have been infected, which is difficult without knowing who is the killer is passing it along.
- Kristin Lehman as Detective Angie Flynn
- Louis Ferreira as Sergeant Oscar Vega
- Brendan Penny as Detective Brian Lucas
- Lauren Holly as Dr. Betty Rogers
- Karen LeBlanc as Detective Paula Mazur
- Chad Krowchuk as Logan Tenwick
- Luke Camilleri as Chris Mancuso
- Brittney Wilson as Kierra Graff
- Matthew Harrison as Rick Morten
- Ted Cole as Kevin Suvanto
- Jennifer Cheon as Janet Tensel
- Emily Haine as Gabrielle Marks
- Paul Herbert as David Brundle
- Cedric De Souza as Dr. Sia
- Eileen Barrett as Librarian
- Vivien Elizabeth Armour as Neighbor
- Paolo Maiolo as Doctor
- Adil Zaidi as Adil the Car Salesman
- Peter Brown as Hipster (uncredited)