When Cera is upset and run away because her father Topsy who mad and yelling at her, she looking for her mother until she meet Sparky the young Threehorn boy and his friends, Tootie, Susie, Kristy, Trip and Ed, and bring her to their family the Unite Herds, lead by Iron the Styracosaurus who has scars on his face and revenge on Topsy. Meanwhile the herds of the what happens, Topsy don’t know where Cera is and why. Littlefoot know about Cera try to tell Topsy about didn’t lose Tricia it was aciddent but he wasn’t listen and mad at her. Littlefoot’s grandpa tells Topsy who get learn to listen to her and children say. If Cera say about Topsy in the valley, an older Centrosaurus named Old Horn tell her the truth about Topsy is a Dark Threehorn and son of Terror who killed all sharpthooths. Sparky learn Cera be nice and not follow her father’s older. When Cera take Sparky and friends, her adopted mother Calar and little adopted sister Tootie to the Great Valley, Cera tell her friends, Littlefoot, Ducky, Petrie, Spike and Chomper, she really sorry about hurt their fellows. So Cera’s friends meet Sparky’s friends, Littlefoot ask Sparky about he lead his friends do right thing and show him look around the Great Valley, but until Sparky saw and meet Topsy who looking for Cera. Littlefoot’s grandpa see Littlefoot’s new friend and meet Old Horn. Later, Calar meet a male Styracosaurus named Styra and ask why he don’t help Topsy looking for, he thing he’s too bossy. Littlefoot tell Sparky about learn everybody become friends between all herds. When Littlefoot and Sparky help pull Susie and Spike out from the cave, Sparky and Cera become like at other. When Sparky show Cera to see stars about everything, Cera wonder about what happen to her mother, as Sparky’s real parents but they’re died when he was hatchling. Cera and Sparky back to Calar and meet Styra who like her, they see Topsy is coming and hiding, Cera hear Topsy tell Tria truth about he lost her mother and siblings. Calar see how Cera’s fell and then back to the Unite Herds, until Iron’s spy Tape the Tapejara saw and hear everything about Cera is Topsy’s daughter, Iron’s plan for get revenge on Topsy when he meets his niece’s new friend Styra. Iron send Styra to warm Littlefoot’s grandpa about Topsy is a Dark Threehorn. Cera, along with Sparky and his friends, must tell Littlefoot, Ducky, Petrie, Spike and Chomper truth about Topsy but one mission: where’s Tootie, they must find her but until Topsy appear. Cera, Susie Kristy, Trip and Ed get hiding but Sparky still shock to say hi to him. Topsy want to talk Sparky how he know about why Cera run away. Tootie look around the valley then she meet Cera’s half-sister Tricia, so Tootie and Tricia become friends. Later, Styra want talk to and Calar meet Littlefoot’s grandpa about Topsy is a dark threehorn when Old Horn hears to tell him the truth. Later Sparky tell Topsy about he hurt Cera’s fella and take him to her, but until Tootie and Tricia appeared. Topsy start to chase them until Cera crab the girls and Sparky fellow them from Topsy to gate of the Mysterious Beyond. The kids are there until Topsy show up. Topsy ask Cera where she been, but until Iron and his herds show up are meet again for long times when Topsy see. Iron start to get revenge on Topsy who did to he has scars on his face and his older brother Steel but Sparky try stop him who hurt Topsy and let him escape before gate are block by rocks. Cera is worred Sparky in other side block but Topsy tell her come and warm herds. In the place of herds, Old Horn has told the herds the truth about Topsy until the herds saw he is coming. Topsy find out what going on, Littlefoot’s grandpa say why Topsy tell them who he is, Topsy say what it talking about, and it was Old Horn who told them about him. Topsy start gets mad at and hurt Old Horn but Styra saved him when Topsy accident get him a scar, just like Steel, and now Topsy is freak out when the herds and Cera shocked and saw what he did just like Old Horn say to Topsy, “You act like your father Terror who careless and killed all sharptooths. Topsy say what he done and start run away when the herds say “How cloud you and why all do this?” and will never agreed with him anymore because he is dark threehorn. Later, Cera was really sad about her friend Sparky and her mother Topsy lost, Calar see how her feel about her mother and tell her about she find and adopted Sparky when he was hatchling. Meanwhile in the block gate, Iron blame Sparky who let Topsy escape and gift scared on his forehead because he think he start to war and then Sparky run away to find another enter to the Great Valley. Iron will thinking to start the war but Tape have good news and tell him about Topsy run away because he did hurt someone, Iron got idea: when Topsy leave the Great Valley to the Mysterious Beyond, the Unite herds grab him to execute him to death and then Iron’s revenge will complete for his brother Steel. Meanwhile, Cera’s friends are mad at and don’t even want to talk to her because her father is dark three and son of killer threehorn and she didn’t mean hurt their feller what say that. Cera, try to say really sorry but her friends’ rejection of her, she’s really sad to cry and leave them and think to find her friend on her own. Later, Littlefoot and Tria see Calar and Old Horn help and make Styra better, Tria apologizes to her friend Calar after she saw what Topsy did and he’s dark threehorn and become friends again long ago. Littlefoot tell Calar, Old Horn and Sparky’s friends about herds become friends because make friends between herds of the and Unite herds for their new home. Later, Sparky finally back to great valley until Topsy who saw a scar on Sparky’s forehead, show up, Topsy tell him tell Cera he really sorry cause hard at her and Sparky will find her for him. Later, Cera was sad for looking for Sparky in everything on the valley, until Sparky see how her fells and she look around to found him, Cera and Sparky become like each others as friendship, see water mirror at them and she say “We are friends”, Sparky thinking about will find and bring him back to the valley when Littlefoot’s right about make peace between herds. Meanwhile, Littlefoot, alone with Sparky’s friends, tell his friends try to find Cera who try saying really sorry and apologizing for being angry and helping her to find Sparky before they ask grown-ups help to find them. Later, Topsy what to choice, leave to mysterious beyond or return to the , suddenly Iron send his herds grab him and find somewhere for execute Topsy. Littlefoot and his friends go to and tell grown-ups, who thinking about Topsy didn’t harm everybody, for help them to find Cera and Sparky, but Tape arrive and say “Topsy will died on his execute by Iron for his brother Steel!” The herds’ shocks hear what Tape say, they must stop them who going killed Topsy and tell the kids stay the valley. Littlefoot and his friends will find away to find Cera and Sparky and stop Iron’s plan, so Calar, Old Horn and Styra will help the kids. Before the Unite herds will execute Topsy, Tape report Iron he saw the herds of the valley try to stop them. Iron says to Topsy “If your own herds try to stop, we’ll fight them.” Iron orders his herds to stop them. The kids saw the grown-ups are fighting each others as war, so Cera and Sparky too. When Iron try to execute Topsy but fight is stop was Cera and Sparky show ups and tell them stop it. Cera and Sparky want to tell grown-ups they say “We are friends mean make peace between us.” like Littlefoot’s say. Calar say the children were right hold time, now all herds will understand what children said. Iron refused what the kids said and order the Unite herds to execute but Tape tell him time out and say “If we’ll fight them, join them in the Great Valley for our new home.”, so Tape and Unite herds to join the Great Valley, but Iron is still angry and blamed to attack Topsy and say “This is for my Steel!” until Styra, alone with Cera accident, stop him to the cliff. Topsy try to save Styra and Cera, so the grown-ups help him. When dangling over storm-swollen water, Styra offers his help, but Iron refuses and falls to his death or survives. When Topsy say Styra and Cera are safe and back to the cliff, Topsy tell Cera he apologizing for to hard and yelling at her and lost her mother when she hear everything he say, she say that’s okay, so the Unite Herds apologizing him for blame him. Topsy say to Cera’s friend Sparky thanks for everything tell her really sorry, so Topsy become friends with Sparky who like Cera. And so the Unite herds join the Great Valley for their new home by Littlefoot’s grandpa accepted them, Littlefoot and his friends were glad all grown-ups are understand and will listen to children. Styra and Calar becomes mate and Tootie and Tricia are playing each others.