The ship was en route to Onderon to deal with the unrest on that world when it was ordered by Admiral Carth Onasi to divert its course to the Outer Rim. Admiral Onasi gave the mission highest priority, and though the captain had doubts about it, Harbinger soon picked up a passenger—the Jedi Exile, recently returned from outside Republic space. With its new passenger aboard, the Harbinger then set a course for Telos, intending to reach the world within ten days. It was meant to aid in the recovery effort on that world
Carth Onasi wanted to talk to the Exile about Revan, so he asked the captain to bring the Exile to Telos but then it encountered The Ebon Hawk which was sending distress signals and claimed to be attacked by a Sith Warship and you know the rest.
Atris took the Exile's return as an opportunity and spread the news of the Exile's return in order to lure out the Sith.
But I don't understand why the Sith Warship attacked The Ebon Hawk in the first place.
(Atris was a schutta, it was her plan to hold a Jedi meeting on Katarr, so the devastation of Katarr was HER FAULT. And she blamed the Exile for the destruction of Peragus. What a hypocrite. Typical Jedi.)