Lou's mother was killed in the Buff Clan attack on New Lopia, and the infant was taken onboard the Solo Ship. He generally caused small-scale trouble, whether roped into a scheme of Ashura's, chasing that blue flying frog around (and inevitably onto Sheryl) or just by totally evading Lin and charging around the ship in his wheeled walking buggy. Lou fell ill with the measles at one point, forcing the colonists to make contact with the Brazilier base. He was cured there, but it meant the hostilities began to head towards Earth.
As the youngest and therefore purest of the Solo Ship's crew, Lou's moods were able to influence the Ide. This wasn't always a good thing, as if Lou was unaware of the danger facing the ship, or far away from the Ideon, the Gauge would often go dormant. However, on the two occasions Lou was taken onboard the Ideon, it gave the robot new reserves of power - the first revealing the Ideon Swords, while on the second occasion the Ideon Gun fired itself to save the crew when the robot was disabled by Rukuku Kil's Freeze Attack.
Sheryl stepped up her research on Lou's relationship with the Ide, trying to find a way to control it through him. She decided on the drastic action of directly threatening his safety in order to invoke the Ide and save the Solo Ship from a collision with a comet. The Ide responded, destroying the obstacle via the Ideon Gun. The blast threw Lou and Sheryl overboard, but the Ide intervened and saved Lou. He began contacting Karala's gestating baby via an empathic link, leading her to rescue him from the exterior of the ship. Lou continued to communicate with the unborn Messiah even after Karala's death.
Lou was the only series regular not given an onscreen death, though presumably he was killed when the Solo Ship was destroyed. His spirit then joined that of Messiah in leading the astral forms of the colonists and the Buff Clan to the reborn Earth.