Elementary's season finale gets darker and more personal when Sherlock's friend and former sponsor Alfredo (Ato Essandoh) goes missing. But has he been abducted or has he relapsed? Neither possibility bodes well for his future, but for now Joan and the police are on the case because Sherlock is occupied with another investigation.

"Sherlock is compelled to keep some bad company," creator Rob Doherty tells TVGuide.com. "The person ... is someone we've seen before and is a threat to him."

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This familiar face will strike a nerve in Sherlock when they travel through dark alleys - both literal and psychological — that test his sobriety. Will the famed detective be able to maintain his equilibrium? Let's just say that we'll see an ugly, brutal side to Sherlock that has been alluded to this season. Sherlock's potential bender sets us up for another visitor from Sherlock's past whom he won't be very happy to see.

Who do you think will be dropping in on Sherlock next year?

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