Kevin and Annie find an abandoned dinosaur egg, which Annie brings home. A tyrannosaurus rex terrorizes the tree house compound and almost eats Tom. When the egg hatches, Annie names the baby dino Tasha It is little Tasha that inspires Kevin on how to chase away the t-rex.
Tom believes there might be other people in the Land of the Lost, so the Porters search for them. In the Process, Tom is bitten by a poisonous lizard. Christa, the jungle girl and Stink, the Pakuni monkey boy emerge from the foliage to help find an antidote to save Tom.
The Porters embark on a scouting expedition in the truck to find a way out of the Land of the Lost. But the truck, with Tasha asleep in the back, is stolen by sleestaks taken to their cave and presented to their leader, Shung.
Tom is obsessed with finding the elusive jungle girl. The Porters locate her cave, but Christa is vary wary. Matters are complicated by a rare confluence of the triple moons, which causes all the animals, including Tasha, to become dangerous. The Porters ultimatley learn that Christa also come from twentieth-century america.
When Shung loses his power crystal, Annie comes into possession of it. The Crystal gives her powers she never dreamed of. But its evil nature is slowly changing her for the worse. Annie ultimately realizes her family loves her just as she is, without the aid of the crystal and, after defeating Shung, she throws it away.
Tom decides Tasha belongs in the jungle, so Annie reluctantly leads Tasha away. Things don't go easily for the little dino and she has several close calls. But when the Porters change thier minds and go looking for her, they find she has learned how to cope and are relieved to know she will do fine when it comes time for her to leave.
A twelth-century knight stumbles into the Land of the Lost and recues Christa from Sllestaks. Kevin who has a crush on Christa, is jealous of the attention the knight recives. Later, the knight commits several blunders and confesses to Kevin he has lied: He is not a knight, just a lowly squire.
When a volcano erupts, Tom assigns duties to everyone, then leaves in the truck with Christa to create a lava dam. Kevin, who resents being stuck near home with a menial task, deserts Annie, Stink and Tasha and goes off with his camcorder. While videotaping the volcano, he gets trapped in a quicksand bog.
Annie resents being the junior member of a male-dominated family and envies Christa's supposedly happy go lucky life. She spends a few days with Christa and in surprised to find that her way of live requires skill and hard work. Meanwhile, Shung finds one of Christa's keepsakes and uses it to establish a hypnotic mind control over her.
A new ""time door"" is about to open up --and the Porters must choose between returning home, or saving their prehistoric pals Stink and Tasha from Scarface, the hungry Trannosaurus Rex.
Returning to their treehouse compound, the Porters find thet land in the grip of a withering drought. But to get fresh water, they must risk exposing their homebase location to the vile Sleestak lizard-men.
The Porters throw Christa a surprise birthday party. Things get hectic when the treehouse is ransaked and Kevin's gift to Christa is stolen. Kevin jumps to the conclusion that Stink was responsible, but later learns that somethig else crashed the party decorations.
The last of the Porters batteries finally dies, leaving them without flashlights, music or any other links to the twentieth century. Tom sets out alone, determined to find a replacement energy source in the form of crystals. This means venturing into Sleestak territory, where he winds up trapped in a cave with Shung.
Annie befriends Keela, a sorceress banished to the Land of the Lost by an evil king. Keela uses her magic to entertain the Porters and turn Tasha into a taking dinosaur. But trouble follows: Keela is being pursued by Magas, a one-eyed beast who had been an evil sorcerer untill Keela turned him into a monster.
The Porters come apon a suburban street, right in the middle of the jungle, complete with their house But the house turns sinister. Tasha is attacked by the refrigerator, the furniture menaces the kids and Tom's leg is pinned by the garage door. They ultimatley discover an old Sleestak machine is responsible for creating the illusions.
Kevin and Tasha find Opah, an old Paku who is Stink's grandfather. Stink is embarrassed by his grandfather's ways, especially his ""musica"", a wooden flute that has a hypnotic effect on the dinosaurs. But Stink changes his tune when Scarface threatens the family and Stink must use Opah's flute to save the day.
Shung uses his crystal on Christa to place her under his control and uses her to summon the Porters. When the family arrives, the Sleestaks capture them and lead them to an amphitheater where they are forced to fight each for Shungs entertainment.
Stink shows the Porters, Tasha and Christa a beautiful beach, but the place makes Christa uncomfortable. While there, Annie befriends a ""fish-man"" creature named Namaki, who helps Christi recall the night she was separated from her family and left in the Land of the Lost.
After an argument with her father, Annie heads for the jungle, where she meets Simon Cardenas, who just arrived from the future. Simon had borrowed his father's time belt to take a joy ride, only to collide with another time traveler, a dangerous alien cyborg. The collision dumped them both in the Land of the Lost.
The Porters, Stink, Tasha and Christa spend the day on the beach with Namaki. But one by one, the Porters vanish without a trace as hypnotic music plays. Namaki, Tasha and Stink search for them and find that the Porters are being held by a shape-shifting siren (imprisoned by a serpent) and she wants them to become her family.
The Porters form an uneasy alliance with the dinosaurs.
Annie leads the group, but is she cut out for it?
The Porters are captured.
The Porters find a sorcerer who has stumbled into the land of the lost.