Eugene was mired in a moral dilemma on The Walking Dead after realizing that Dwight had helped Rick. Negan had previously told Eugene that his life depended on outing the traitor, but Eugene had second thoughts.
Eugene confronted Dwight, saying,"I need you to cease and desist all betrayals and back-stabbery, fronting and Judas-ness A.S.A.P. I offer to keep what I know from Negan and the others."
As long as no one got hurt, Eugene was happy keeping the secret. This was big for Eugene considering he described himself saying, "I am a small person who does not stick his neck out for anyone other than himself. I stick firmly within my lane without any need for a signal, hand or automatic."
To make matters worse, Daryl drove a truck into the Sanctuary. This allowed the walkers to enter, and in turn trapped the Scavengers on the second floor.
Eugene convinced Negan that he had plan to help them escape and that it required lots of bullets. While the audience was not informed of the exact plan, it is assumed that it worked because by the time Rick arrives, the place is deserted.
Speaking of Rick, he finally convinced Jadis to join his team. But the treaty was dependant on the Sanctuary still be under siege by the dead. Which means Rick has a lot of explaining to do in next week's final episode before the mid-season break.