Lucy Liu, Jonny Lee Miller

Elementary's Sherlock Holmes is the best detective in the world, which means it shouldn't be long before he uncovers Watson's little secret: She's lying about her employment status so she can continue being his sober companion.

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Following Sherlock's (Jonny Lee Miller) run-in with Sebastian Moran (Vinnie Jones), Joan (Lucy Liu) decided to ask Sherlock's father for an extension on their contract. But when he denied her request, she lied to Sherlock in order to stay during his time of need.

"It's not a lie that Joan is going to live with for a particularly long time," executive producer Rob Doherty tells TVGuide.com. "It's something that we expect to get around to in the next three or four episodes."

Naturally, once Sherlock finds out the truth, it will initially cause a divide between him and Watson. "The expectation would be that Sherlock would feel betrayed and upset and embarrassed," Doherty says. "He was so resistant to the idea of Joan in the very beginning. He did not think he needed help. He's learned over time that it's a good thing to have her around."

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Yes, Sherlock has come to realize how much he needs Watson, but has Watson come to see how much she actually needs him? "Her therapist asks her that point-blank," Doherty says. "The funny thing is that it's a question that won't actually make it to the episode, but there will be an interesting conversation about it and why she did it. I'd say the more important question is: What is Joan to Sherlock in the wake of that revelation?"

Elementary airs Thursdays at 10/9c on CBS.