If I was involved to the depth you seem to be, Robert, I would decide first if any of the negatives might be valuable either personally (I have images that mean a great deal to me) or commercially and set the list out for scrutiny. You might consider negotiation for the valuable pieces and hand over the remaining without charge. Or just give the whole shebang to them and make them both sign a detailed receipt with the restriction that there be no further dealings. I think you might do well to contact an attorney, just in case.