William Petersen: We finally have sex? Believe me, it’s been brewing all along. For me, anyway. Marg Helgenberger: Catherine would love to have a roll in the sack with Grissom! Petersen: They have this understanding with each other. There’s a different kind of respect Grissom has for Catherine that would preclude a relationship on that level. The very thing that was wrong with Grissom and Sara is what he wouldn’t allow to happen with him and Catherine.