Complex sentence: Fry is loath to trust a vicious criminal like Riddick, but his claims prove true and she confronts Johns, discovering that he is also addicted to morphine stolen from the ship which could've lessened Owen's agony before his death.
Split into simpler sentences: Fry is loath to trust a vicious criminal like Riddick, but his claims prove true and she confronts Johns, discovering that he is also addicted to morphine which he stole from the ship. The same morphine which could've lessened Owen's agony before his death.