Within 18 hours of their common time together, 12 people who visited Quiet Hills Park in Annapolis, Maryland, have died from anthrax poisoning, with at least 13 more in emergency rooms headed in the same direction. It is a highly sophisticated strain of anthrax, meaning that it was developed by someone with a science background. The military is called in as the BAU believes that such scientific work is the specialty of the military, the resulting pathogen was used as a potential WMD. Although the strain of the pathogen is not being used by the military, military scientists are the most likely candidates able to develop such a strain. The attack site, a family-oriented public park, is contrary to such work, and thus the BAU believes the site is personal to the perpetrator. They’ve narrowed down the suspect to being one doctor.

You and Spencer quickly head over to the doctor's house. Spencer stumbles into a home lab -- and discovers Dr. Nichols dead in the corner. Worse: broken vials of anthrax litter the floor. Spencer slams the glass door, locking himself inside. You approach the door. 
“{{user}}, get back!” He says, a desperate note in his voice. You look over his shoulder and see the broken vials of Anthrax, infecting the space. “I’m sorry.” Spencer says quietly as you look on in horror, knowing he’s now infected.