"Solve for X" was another of Elementary's unique episodes. This one centered around a circle of genius mathematicians working to solve one of the worlds hardest equations, P versus NP.

All the while, we got a glance at Watson's past and it was - sorry to sound corny - beautiful. Lucy Liu was terrific as always, with the series taking a major step in the right direction by actually focusing for a change on Watson.

Before I talk about Joan, though, let's start at the beginning.

We open up with a mugging where mugger ironically gets shot while begging for his life the same exact way, begging just like his victim. Karma is a bitch, isn't it?

Tonight noticeably featured more Detective Bell. I was wrong last season when I said I could care less about his character because here I rather enjoyed the role he played. I don't mind seeing more of Bell and less of Gregson. Even though Gregson looks super handsome with his new hair cut.

During the investigation, the team uncovered the whole reason why two men were murdered: Math. No, not meth. MATH.

Math rules, right? A nice comedic touch was seeing Harlan work on the P versus NP equation shirtless with the possibility of going completely nude because he doesn't want anything to interfere with his work. But, remember, he would have had to ring a bell first.

Through the twists and turns of the investigation, it seemed that no one actually solved the P versus MP equation until Tanya got busted at happy hour. Sorry, Lynn Collins (AKA Kyla Silverfox), but Sherlock Holmes got ya.

The dynamic duo strikes again! Was anyone else incredibly proud of Watson being able to pinpoint the differences in the handwriting on the P versus NP black light equation?

Moving on...

The biggest part of the episode centered around Joan and the guilt she carries with her. This guilt comes from a patient that she killed on the table, the whole reason she stopped being a doctor.

This is where we dove into Joan's past for, truly, the first time. We've met her parents, found out she slept with one of her old companions, you know little things. But what we have never done is delve into what happened and what went wrong with her last surgery.

Well, we knew she accidentally killed a man. In Sherlock's words, "accidents happen." This accident was something she has never truly been able to move on from.

To put this storyline into motion we met Joey Castoro (played by Jeremy Jordan), the son of the man that died on her table. We see that he is asking Joan for money - again - and the guilt that Joan carries with her makes it easy for her to give it to him. She actually forked over a car the last time this happened.

Sherlock saw right through this act, though. From the beginning, he knew Joey was trying to take advantage of Joan and he had a big problem with that. So big he gave Joan $22,000 to settle with him.

I was really proud of Joan at the end when she decided to invest in his education and not his bar, this was the best part of this whole storyline for me. To me, Sherlock helped this plan set in motion by questioning Joey's motives, showing true concern that she was possibly getting taken advantage of.

Then there was scene at the very end between the both of them, with Sherlock wanting to go to the cemetery with Joan because the man she accidentally killed made quite the impression on her. Sherlock cares so much about Watson, whether it be platonic or not. And just think: without his unfortunate death, Sherlock and Joan would have never met.

I'm still having a hard time grasping the whole, "there's no romantic interest" in this pairing. All of the signs, the dialogue, the comfort these two have around each other is still making me believe that they should go there.

Here's the odd thing: I wouldn't be upset if they never took it to the next level and I wouldn't be surprised if they did. I love these two no matter what kind of scenario you put them in.

This was icing on an already delicious cake. I can never get enough of back-story from characters I into whom immersed. So, please keep giving us more of this because it really does work. Especially when you have two great actors who can pull you into a scene and not let go.