The central plot twist of "Lion" is not a twist of events, but a gradual revelation of memory and truth. The entire second act is a painstaking process of Saroo using Google Earth to find his home. The breakthrough comes when he finally recalls the correct, though phonetically similar, name of his hometown: he remembered "Ganesh Talai," and upon finding a location called Ganesh Talai near a landmark he recognized (rock formations where his mother worked), he is able to trace his way back.
Upon returning to Ganesh Talai, Saroo finds his childhood home is now a goat pen. However, an older man recognizes him from a photo and leads him to his mother, Kamla, resulting in a profoundly emotional, nearly wordless reunion. The most heartbreaking revelation comes next: Saroo learns that his beloved older brother, Guddu, died the very night they were separated. Guddu was hit by a train while walking along the tracks, which is why he never returned for Saroo at the station. This discovery re-contextualizes Saroo's entire journey, infusing the joy of his reunion with the deep sorrow of this permanent loss. The final piece of the puzzle of his identity is the revelation that his name isn't Saroo; he had mispronounced it as a child. His real name is Sheru, which means "Lion," giving the film its powerful, titular meaning and bringing his quest for self-discovery full circle.