There were certainly several what-the-hell? moments in this episode. The first being when the DNA lab exploded in a ball of flame, sending poor Greg flying through a glass window. The second was Catherine's revelation that it was in fact she who blew up the DNA lab. And the third was when Sara bite the bullet and finally asked Grissom out; even if she didn't get quite the answer she wanted.
This episode was very exciting, but the drama took second place to the character development that was taking place. Grissom is at one of the most human he has ever been around his staff; his concern for Greg when he is being wheeled out on the gurney, his defence of Catherine when it transpires that she blew up the lab and most tellingly, his feelings for Sara when she has been hurt. In a season that has done an excellent job humanising Grissom, this episode really showed him at his very best and finally cracked the lid on his cool, professional demeanour.
We also see Sara develop in this episode, particularly through her feelings for Grissom. And after her frightening experience with the lab explosion, we see Sara deal with it by becoming a little reckless.
Catherine too, grows as a person. She is the woman who is used to being right and in charge, and yet in this episode we see her admit that her daughter is a little out of control and that she blew up the lab. Catherine also proves herself to be a braver person than I had ever given her credit for by going to see Greg in the hospital to confess to him that it was in fact her fault the lab blew up.
One of my all time CSI favourites, and always will be.