Hannah Gregson finds her roommate Mattie strangled. Sherlock thinks the killer dressed her in clothes that weren't hers, decorated for Sherlock and Joan. He proclaims that Mattie's murder is a serial killer announcing himself. Ten of the items on Mattie came from murdered women. The woman that bought the earrings found on Mattie's body is Polly Kenner, the same missing woman Michael asked Sherlock to find. Sherlock tells Michael that he thinks Polly is dead. Sherlock tells Joan that he's sure Michael is the killer. Gregson figures out that Michael was the man who hit Hannah's car. Michael invited Hannah out for coffee to get her out of the apartment so he could kill Mattie. Joan goes to get Sherlock's prescription filled while on stakeout, then Michael comes up to Sherlock's car, then they disappear by the time Joan gets back. Michael takes Sherlock to the hospital after he passed out. Michael said he had Sherlock look into Polly's disappearance for his own good, but the previous murders were for Michael's benefit. Michael says the murders were his attempt to replace the high of drugs. Michael said that he and Sherlock need the challenge of vying against each other. Sherlock uses his phone call with Michael to locate Polly's burial plot, on one of MIchael's firm's construction sites. Instead, they find a mannequin. An exhausted Sherlock tells Joan he's going home to rest, but he goes to a club instead to score heroin. Sherlock bought the heroin for Michael, to throw him offstride. Joan goes along with his plan. From a bus, Michael calls Sherlock to tell him he's left New York for a while. So Sherlock takes a vacation to Nepal.