Elementary - Out, and not Union Friendly...

Serials killers always seem to give even the best detectives a run for their money. Sparing the psychological advantage normally accompanying a serial killer, Holmes ferrets out a killer with a pattern with noticeable difficulty. He and Watson become closer still, but hopefully the villains continue to be strong so the duo are required to pull out more than triggered inspiration to solve cases.

Elementary "On the Line" (S02E09): On the Roosevelt Island bridge, Holmes and Watson are called in to... confirm a murder? The victim (Samantha) called in and told 911 who was about to kill her, Lucas Bundsch, the same man she believed killed her sister. Holmes quickly claims she shot herself, attaching a weight to the gun to drag it over the railing and into the river. Upon questioning Lucas at the station under a polygraph, Holmes injects a question of his own and proclaims the man to be a serial killer.

Holmes shows how Lucas beat the polygraph on key questions, guessing he also had to fake answers about the previous murder. Holmes nettles the detective, Coventry, on the previous case, to the point of a shouting match in the middle of the station before Captain Gregson breaks them up. The duo analyzes the last traffic camera footage of Samantha's sister and guess that the killer made a fake plastic explosive to place in her shoe while she phoned her sister.

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In the middle of the discussion, Lucas shows up at the Brownstone. Allegedly given their house address by Coventry, Holmes surprisingly invites in Lucas and starts to question him about the abduction. In a creepy, unemotional scene, they confront Lucas and listen to him deny the entire thing.

At the station, Holmes and Watson present their case and links to other murders they think Lucas committed. Gregson agrees there's something to it and Watson insists the duo split up to investigate the potential victims. She and detective Bell question a loved one of a victim whose body was never found, learning nothing. Gregson tried to calm down Conventry, but he threatens to call the union over Holmes' involvement in his case.

Holmes and Watson get into a tiff about his treatment of policemen and their growing dislike for the duo. The person Watson interviewed calls with a lead: a woman in his support group recognized Lucas as her missing daughter's ex-boyfriend. The duo head up to Syracuse to meet with the woman, but discover they've been fooled by Lucas. He made up the fake story and pretended to be the victim's mother, who in reality has no children.

Holmes confronts Lucas about making the fake profile about the missing girl to join the support group and falsely leading them to Syracuse. Lucas riles Holmes up and Holmes punches him, prompting a restraining order against him and Watson. Gregson kicks Holmes off the case, and Watson discovers Holmes broke a finger with the punch.

After Lucas abducts again, Lucas texts Holmes the address of his victim. The duo goes but Bell sends them away. Holmes grabs some DNA from the scene before leaving so he can frame Lucas, though Watson talks him out of it and accidentally helps him deduce where Lucas keeps his victims: his recording studio.

Gregson, Holmes, and various police show up to raid Lucas's studio and find not only the latest victim but also the wife of Watson's interviewee. Gregson tells his troops to lay off complaining about his employ of Holmes and Watson. Holmes tries to convince Watson he's acerbic and will never change because it's an advantage for him, and it's only Watson who is the exception to his behavior because he finds her exceptional.