At the start of the movie, Garth is originally engaged to marry Lilly's older sister Kate in order to unite the packs. When she first met Garth she immediately found him attractive, however at the time Garth didn't show signs of having feelings for Lilly as he was focusing on his duty to marry Kate for the packs. Eventually though when Kate went missing, Lilly offered to show Garth around and soon they began to fall in love with each other. They did many activities together such as when Lilly made Garth laugh with her turtle impressions while Garth showed her some hunting moves. When he tried to teach Lilly how to hunt, she missed the target and instead crashed into a log, Garth helped Lilly by bushing her hair out of eyes so she could see better. When Garth first saw Lilly's eyes he commented saying they were beautiful.
Later in the movie, Lilly helped Garth by teaching him how to howl (howl in the series is also known as singing), where he gained a beautiful voice and they sung together. However they were cut short when Garth noticed the Eastern Wolves approaching, telling Lilly to run, where she soon informed her father of the upcoming attack. However, the attack was soon called off once Kate and Humphrey came back, but soon both Lilly and Garth became heartbroken as now Garth and Kate had to get married in order to settle the dispute between the packs once and for all. During the ceremony, Lilly was in tears the entire event as it was heartbreaking for her to witness the wolf she loves marrying her sister.
Later when the mating ritual was about to be completed, Kate couldn't bring herself to complete the ceremony and soon she had admitted she had fallen in love with Humphrey, an Omega Wolf. Garth's father Tony was outraged saying that love between an Alpha and an Omega was against pack law, however much to the surprise of everyone, Garth also confesses he had fallen in love with Lilly, much to her delight. Eventually at the end of the movie, Winston and Tony allowed Garth and Lilly to marry along with Kate and Humphrey.
Other wolves talking about Lilly and Garth. In this scene we learn that Lilly and Garth live in tall grass, but we don't see this place. Next Garth goes to the war and Lilly was told to stay at home but follows along despite him telling her it would be dangerous. Later in the movie, Garth, Winston and Tony meet up with Kate and Humphrey. They come up with a plan to distract King. Humphrey stands on Garth's back and pretends to be a large alpha whilst Kate rescues Runt. When King realizes it was a trap, he sends his pack against them. The trio retreat (along with Runt) back to Tony and Winston. They realize they cannot beat Kings pack, but they acquire the help of some bears.This leads into a fight scene. When Garth gets backed into a corner by 3 wolves, they start to mock him for marrying an omega until Lilly rolls a log off the edge of a cliff and traps Kings wolves under it.
Lilly and Garth are not featured or mentioned in this movie.
Lilly and Humphrey take the little omegas into the 'haunted' forest. Once inside, they are confronted by two porcupines, warning them to go back, but Humphrey said 'But the forest is that way'. We see them outside Saw Tooth Cave, when Runt climbs a tree and sees a 'ghost'.