I don't think it's that. It almost seems like they may be in trouble with the law and I can't help but think that it has to do with this plan with Luca after all "Murder She Wrote" is the episode title for the one before the episode description where it says that Joss scrambles for evidence against Calista.

I really liked Calista so I don't like the idea of her trying to throw Joss under the bus for something.