Complex sentence: Mutual distrust of both sides gradually subsides; the truce is endangered when Carver threatens Caesar's sons with a concealed shotgun, but the two sides reconcile when Ellie offers to help treat Caesar's ill wife Cornelia with antibiotics.
Split into simpler sentences: Mutual distrust of both sides gradually subsides but trust momentarily ends when Carver threatens Caesar's sons with a concealed shotgun. The sides reconcile and Ellie is allowed to treat Caesar's ill wife Cornelia with antibiotics.