Captain Ventralis mentions Han if Commander Shepard asks what happened in the hot labs; Ventralis explains that Han was the only survivor of the rachni attack and "he ain't all there any more". Dr. Palon asks Shepard to be considerate to Han because he has been through a terrible experience.
Han is severely traumatised by his experience and answers Shepard's questions monotonously. He tells Shepard's squad that he knows they are there for the rachni, surprising them due to the rachni's believed extinction. Han Olar explains that Binary Helix found an ancient egg, aboard a derelict vessel drifting in space, from which a Rachni Queen hatched. In retrospect, he believes it might have been a mistake. Two other scientists across the room tell him to shut up and stop talking about confidential information: "If you're going to be crazy, be the quiet kind!" However, Han no longer has an interest in keeping Binary Helix's secrets, stating that he has no control over who lives or who dies.
When Shepard asks how he survived the hot labs, Han answers "I killed her," much to the shock of the squad. He explains that he and a co-worker, a female scientist, were going to lunch when the alarms went off and the rachni escaped containment. Han managed to get to the tram tunnels, reach the train and close the door behind him; he describes the gory death of his colleague without emotion.
If Shepard makes the biotoxin cure and is ambushed by Alestia Iallis, Han points the Commander to the maintenance area where the geth came from, and suggests they ask Dr. Zev Cohen for a pass in order to enter there. If Shepard clears the hot labs first and returns through the scientists' quarters, Han is seen being threatened by Benezia's forces and he asks the asari commando threatening him if he'll get a "you know too much speech". After killing the asari commandos, Han tells the Commander that he's the only one left and that Ventralis had everyone killed under Benezia's orders.
Mass Effect 2Edit
If Shepard met Han on Noveria in 2183, he sends Shepard a message, entitled "Therapy":