The "Elementary" episode "The Deductionist" centered on an escaped criminal. This installment was different from the usual Sherlock-Watson relationship arc episode. In fact, there was not much about their relationship at all. Rather, the subplot centered on the relationship between Sherlock (Jonny Lee Miller) and FBI profiler, Kathryn Drummond (Kari Matchett). The other subplot followed a humorous situation involving Watson (Lucy Liu) being kicked out of her sublet apartment because of a pornographic movie.
A dangerous criminal, Martin Ennis (Terry Kinney), escapes by faking an IV that is meant to put him to sleep. He was supposed to be donating a kidney to his dying sister, but instead slits the throats of innocent people who are trying to save his sister's life, stealing a gun in the process.
Drummond, who was responsible for capturing Ennis the first time, is called in on the case. Sherlock claims to hate profilers, but he finally admits to Watson that he had slept with her. Watson still can't understand why he hates her so much until Sherlock further explains that she profiled and betrayed him. She was only in a relationship with him so she could find out what he was like, then tell the world about it in a book. The real clincher of Sherlock's hatred was that she seemed to predict his drug addiction before it happened.
Just when they think they've got Ennis all figured out...
Initially, Sherlock and Drummond both agree on what Ennis may be up to. But then he goes and does something that completely blows his profile out of the water. He plows down everyone in a liquor store, leaving a single young blonde woman (his usual target) alive. Drummond initially tries to explain it away as necessity: He hit the liquor store because he needs money, but that doesn't explain why he killed everyone but the blonde.
Watson postulates that Ennis is trying to confuse law enforcement. Sherlock agrees that he's trying to throw them off. Their theory is partially confirmed when Ennis calls the police. He's not just trying to confuse the police, but to invalidate Drummond's profile of him. He'll stop killing as long as he can have Drummond all to himself!
It turns out that Drummond is not such a nice FBI profiler. She created a profile of Ennis that was based on sexual abuse. She thought he had all the classic symptoms of such abuse and faked a witness to "prove" that she was right. When her book about Ennis went public, his entire innocent family was destroyed. Ennis just wants payback for his family. In a sense, Drummond is partially responsible for Ennis's killing rampage! It's not very smart to anger a serial killer.
It turns out that the sister was poisoning herself on purpose. Although she was initially innocent, she wanted payback for her father's suicide and mother's death. She lures Drummond with information about her brother, then stabs her with scissors. Sherlock and Watson deduce that the sister is in on it, but gets the call in to Det. Bell (Jon Michael Hill) too late. Fortunately, Drummond survives the attack. Hopefully we'll see more of this character, as her relationship with Sherlock is spicy and filled with some amount of hatred.
Sherlock really does have Ennis figured out (sort of)
Sherlock brilliantly deduces Ennis's location based on how he had his radio tuned. Sherlock then discusses how he was also wronged by Drummond. He lays two objects on a table and gives Ennis two options: take the cuffs and be a coward, or take the gun and be brave. If he takes the gun and shoots Sherlock, it proves that Drummond was wrong about both of them, including her prediction of how Sherlock would die. Consequently, Ennis grabs for the gun, at which time Sherlock breaks Ennis's hands with a big stick. Earlier in the episode, Sherlock was practicing his stick fighting with a dummy. It really came in handy!
Perhaps Drummond was wrong about everything
Watson explains to Sherlock that Drummond may have lied in her prediction that he would become a drug addict. It could have been a coincidence that she was actually correct. After all, he recovered and made a friend. Drummond had said that Sherlock was incapable of making friends. Of course, Sherlock doesn't initially realize that he has a friend until Watson claims that she is his friend. Sherlock does hide his emotions very well.