It was likely at this time Yarrow became an Imperial spy who answered directly to Darth Vader. Under the alias of Flame, she set up Operation Moonstrike, a plan that appeared to form a major Rebellion. However, this plan was actually part of Operation Twilight, a scheme to eliminate many resistance leaders all at once.
Yarrow met up with Ferus Olin and his group, befriending them and gaining their trust. After many months together, Flame eventually proposed the idea of gathering all major resistance leaders and moving them to Ferus' base. When the ships were nearing the asteroid base, Yarrow was discovered by Olin. Due to the influence of a Sith holocron, Ferus ordered for her execution, but it was later decided that she was to be left on the uninhabited moon, XT987. Although Yarrow was discovered, operation Twilight was a success; all resistance leaders were destroyed by the superweapon attached to Vader's Star Destroyer. However, Ferus, Trever and Lune managed to escape.