| Episode cast overview, first billed only: | |||
| James Roday Rodriguez | ... | Shawn Spencer (as James Roday) | |
| Dulé Hill | ... | Burton Guster | |
| Timothy Omundson | ... | Carlton Lassiter | |
| Maggie Lawson | ... | Juliet O'Hara | |
| Kirsten Nelson | ... | Karen Vick (credit only) | |
| Corbin Bernsen | ... | Henry Spencer | |
| Ernie Grunwald | ... | Donny Leberman | |
| Cullen Douglas | ... | Dr. Tony Mallon | |
| Liam James | ... | Young Shawn | |
| Judd Nelson | ... | Dr. Steven Reidman | |
| Sage Brocklebank | ... | Buzz McNab | |
| Dmitry Chepovetsky | ... | James | |
|
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Dru Williams | ... | Bartender |
| Chasty Ballesteros | ... | Melissa | |
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Stephanie Nudd | ... | Jennifer 'Ginger' Cotsitas |
A murder in a convenience store leads Shawn and Gus to believe that the victim contracted a deadly experimental virus, and not only seek to find who's behind it but believe they also hold the cure to it.