The Leviathan title suggests a monster, an unconquerable beast. This week, Sherlock Holmes is faced with a beast of a case: an uncrackable vault and two separate teams of thieves who figured out how to break it.

Casterly Rock Security, maker of unbreakable bank vaults including their latest model "Leviathan," hires Sherlock to look into a heist. The company president is clueless as to how the criminals managed to break into their vault, and are worried its sterling reputation and hefty price tag will take a tumble if word gets out.
One member of the crew who was behind the original 2010 heist lets on that the four were brought together with specialties -- each person had a singular job and weren't aware of what anyone else was doing. The only lead he can muster is that the person who got the gang together was known as "Le Chevalier," a legendary master thief famous not only for the priceless artifacts that he has stolen but also for the fact that he's never been caught. Of course, he was never sought out by Sherlock Holmes...
Meanwhile, Watson attempts to win over her hard-to-please mother. She looks down on her daughter's occupation, comparing it to babysitting and chiding her for not being able to break away from the addict of the month to spend time with her visiting brother Oren. In an enlightening scene, Holmes talks Watson up to her family, praising her for her role in catching criminals while helping him rebuild his own fractured life.
The case is a nice break from the typical murder investigation (well, at least initially) and presents one of the more intriguing puzzles of the season so far. It also drops a few interesting facts our way, like that bone marrow donation recipients actually manufacture blood cells bearing the DNA of our their donor. Definitely one of the more compelling stories we've been treated to on "Elementary," and I look forward to more.
Final Grade: A
This Was a good episode and a true puzzle. I'd heard the fact before about the bone marrow( surely from another crime drama) but had forgotten it. Just goes to show you that watching tv can indeed be educational:)