Dr. Gary Guzzo was brought over to the Destiny, through use of the Long-range communication stone, to aid the ailing Lanteans. He believed they were suffering from a flu or cold bug, or something similar that either one of the Tau'ri or Lucian Alliance members brought onboard Destiny. The reason the Ancients are so effected by it is due to the them having been in stasis for so long, their immune systems have missed out on the bacteria's evolution. In order to help them, he suggested Tretonin. (SGU: "Back to Destiny 3")
While waiting for the Destiny crew to acquire the needed resources for him to make a synthetic Tretonin, Dr. Guzzo aided Lt. Tamara Johansen in making Vasi and the other Ancients more comfortable by relieving their symptoms temporarily. (SGU: "Back to Destiny 4")
In the end, Dr. Guzzo was successful in making a synthetic Tretonin and curing the Ancients. He left the Destiny crew with the knowledge of what materials they'll need to look out for, to keep them supplied. He informed T.J. he would visit again to check up on them later. (SGU: "Back to Destiny 6")
- Visually, Dr. Guzzo changed as Back to Destiny progressed. He was first introduced as a man with white/grey hair, a widow's peak, and dark brown eyes. By the end of the volume, he looked younger, had vivid blonde hair, no widow's peak, and his eyes appeared grey blue.
- This could be because he was using the Long-range communication device, and one of the men might be the host's body, or both could have been two different hosts.