Complex sentence: When Moreau discovers that Parker found out about Lota's nature because she is starting to revert to her panther origin, he despairs, believing he has failed--until he notices Lota crying.
Split into simpler sentences: When Moreau discovers that Parker found out about Lota's nature because she is starting to revert to her panther origin. Moreau is stricken with despair, thinking that he has failed--until he notices Lota crying.