Stella and Danny discover the world of cuddle parties: non-sexual events where adults touch and hug each other. Meanwhile, Mac, Hawkes, and Flack investigate the death of a hated plastic surgeon found covered with lye with thousands of eyewitnesses during rush hour at Grand Central Station. Mac and Stella begin to assist Aiden in a rape case, but after it is learned that she broke an evidence seal, Mac must come to terms with this and work up the nerve to fire her.