Gregson and Sherlock investigate when Detective Bell is attacked on Elementary. "Details" is the 15th episode of the show's first season.
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Elementary Season 1 Episode 16 Quotes

[To Bell] How many times did you two have sex? My guess is 9 or 10 times.

Sherlock

If something were ever to happen to you, I am not sure I'd be able to forgive myself.

Sherlock