Dov and Chloe respond to a call to assist paramedics who are trying to take a woman who appears to be on drugs but her husband refuses to let them saying she doesn't take drugs. But they tell him she has to be taken to the hospital to be sure. They ask him where she got the drugs, he says he thinks it's an acquaintance of his wife who owns an art gallery. McNally and Cruz go to check the guy out and they find him, passed out, with face in some drugs. When they wake him up, he throws the drugs at them but collapses. They have the man taken to the hospital. But they learn that the woman who was brought in, is not suffering from a drug overdose but is infected with anthrax. So McNally and Cruz have to remain till a hazmat team can check them out. In the meantime, all the cops try to find out where the anthrax came from. They start by tracking down the dealer who sold the guy his drugs because they believe the drugs were contaminated.