The sex is good, as always. A bit rough, but that is how they both like it. Urgent, intense. As always, they leave their mark on each other. A bite, a scratch, a bruise - anything that will remind the other of it all the next day. Sara knows Catherine will hide hers tomorrow, and Catherine knows Sara won't. Afterwards, they curl up around each other and go to sleep, the way they always do, three or four nights - or mornings - a month. They will have sex again in the morning, but it will be gentle and slow, loving. Still, they both know that when it's over, Sara will go home, to Grissom. She always does. They wouldn't want it any other way.
So, how does Grissom feel about Sara and Catherine? He knows about them, of course. Has known all along. He knows about the odd attraction, the desperate need they have for each other. When Sara comes home smelling of Catherine, with bite marks or scratches on her body, all he can do is hope she knows what she is doing. Sometimes the idea of what Sara and Catherine do together turns him on, and he wishes they would let him join them or at least let him watch. They won't. He doesn't really understand what it is they give each other - or what they take from each other. All he knows is that Sara needs it, that she would not be the same without it. So he will let her keep on doing it, keep those nights with Catherine, because he knows that if she doesn't, he will lose her.