In a jeep, Nigel goes through the Time Portal to the Cretaceous in Texas, where Dallas is now. At this time North America is divided into three land areas by a Y-shaped internal epicontinental sea. The land around the Time Portal exit point is dry: gravelly sand with patches of trees and bushes. A pair of half-size juvenile Parasaurolophus go by and stop about 10 m away. Nigel chases them towards the jeep. Then a pair of Albertosaurus appear. The Parasaurolophus honk and run away. Nigel revs his jeep's diesel engine: that makes the Albertosaurus back off, but not for long and they get accustomed to the noise (and presumably to diesel exhaust smell). He drives away. They chase him, at speed up to 30-38 mph, but they tire and turn away.
In the park, Bob is planting young trees to help feed the titanosaurs: he says that he will have to plant 2000 trees each year for this. The titanosaurs, of course, are no help whatsoever at this and keep trampling trees down.
The Smilodon have bred and now have two cubs. Suzanne sees that their mother is not making enough milk for the cubs, so she has to take the cubs and bottle-feed them, thus breaking the natural mother-cub link. If she were to put them back into their mother's enclosure, they would be killed.
On-site, Nigel drives onto a sea beach and looks out to sea for signs of Deinosuchus which could survive for a limited time in salt water like modern saltwater crocodiles. A herd of Parasaurolophus runs past. They are each 10 meters long. He shouts at them to clear off in case they damage his jeep's paintwork. He finds a conch-sized gastropod shell and makes a hole in it and blows it to try to have an exchange of vocalizations: they make noises using their hollow crests.Nigel, with binoculars, sees 5 Nyctosaurus fly in from the sea. They fish by skimming the lower jaw through the water surface. Nigel has brought a microlight with him: he uses it to fly with the Nyctosaurus. A Deinosuchus reaches its head out of the sea and grabs one of the Nyctosaurus. Nigel sees another Deinosuchus swimming from the sea up to a river and decides to head in that direction.
In the park, Susanne visits Martha the mammoth. Martha tries to be an "auntie" to the elephant herd's matriarch's calf. The frightened matriarch drives Martha away. Martha is becoming isolated again, and there is fear that she will again stop eating.
On-site, Nigel paddles in a red inflatable boat on the river. A Deinosuchus bites the boat's stern, does not like the taste of rubber, and let's go. It snaps out of the water again by the boat, then disappears. Nigel paddles two miles upstream to a freshwater lake, where he sees some Deinosuchus on a sandbank, and a herd of Parasaurolophus forced by thirst to come to the lake to drink. Nigel paddles to the other side of the lake. He mentions that Deinosuchus will (geologically) soon be wiped out when sea floods the area, as they have a specialized lifestyle, so he must rescue one. An unwary young Parasaurolophus goes to the lake to drink. A Deinosuchus rockets out of the lake and grabs it by the chest. The two roll over and over in the lake. More Deinosuchus swim in. They take turns to hold the kill while another tears at it.
In the park, the Phorusrhacos has developed a habit of dust bathing near its enclosure's fence, undermining it. Each time, Bob fills the resulting hole with big stones. He realizes that this tactic is only "firefighting" and that he will have to make a new fence with the bottom ends of all its posts buried four feet deep.
On site, Nigel has made a long double row of wooden posts ending in a blind end. He plans to entice a Deinosuchus with meat up the fenced route to the blind end. To get back to the jeep, he walks through a dense forest, but he is worried about dangerous predators. Something is following him. He feels relieved when a Troodon sticks its head up out of bushes and shows that it is much smaller than an Albertosaurus. When he reaches the jeep, he sees that three Troodon are eating the meat that he had brought as bait. He chases them away using a portable aerosol-like horn.
In the park Bob is shoveling up Elasmotherium dung when he sees the Phorusrhacos looking at him through a fence. He calls on his walkie talkie that the Phorusrhacos has escaped again. A keeper comes in a jeep, and by towing some meat behind the jeep leads the Phorusrhacos back to its enclosure.
On site, Nigel plans to use the rest of his meat to bait a Deinosuchus up the stockade. He sets the bait at the stockade's end. They rig hammocks. It gets dark. With his helmet headlights, he sees that some Troodon was pulling away his bait. When Nigel chased after it, another came and ran off with the rest. The meat that was left was not enough to lure a Deinosuchus. They go to bed.They are woken in the morning by the noise when three Albertosaurus kill a Parasaurolophus. Three Deinosuchus come out of the lake to steal the kill. There is noisy confrontation and some biting, and tugs-of-war over the flesh. The Albertosaurus admit defeat and back off.
In the park Martha the mammoth is still isolated from the elephant herd.
On site, Nigel must use himself as bait. He wades into the water and splashes it hard with a paddle until a Deinosuchus investigates. He backs off too soon; the Deinosuchus backs off. He splashes again. The Deinosuchus charges out of the sea and chases Nigel, who runs up the stockade path and at its blind end squeezes between two of its posts. He and 4 men with him struggle to hold the stockade posts upright, until the Deinosuchus tires, as cold-blooded reptiles tire quickly. They set up the time portal close outside the blind end of the stockade. Nigel in the jeep tows three of the end stockade posts out and through the Time Portal; the Deinosuchus is confined too closely to turn round, so it must follow him through the portal. It is enticed with a piece of meat to its pond (made close by the time portal), which it goes into.In the park Bob as usual has to "pick up the pieces". He drives the jeep to his next job, and mutters that Prehistoric Park needs more keepers, as they have so many problems: the Phorusrhacos escaped its enclosure again; the Smilodon cubs have had Suzanne up half the night, the titanosaurs eat too much, and to make matters worse, their digestive systems cannot handle the modern vegetation resulting in bad diarrhea, and Nigel constantly bringing back more creatures is not helping. Suddenly, a Troodon emerges from the kit on the back of the jeep: enticed by the meat in the jeep intended to lure the Deinosuchus, it has stowed away. It snaps at Bob, and the swerving jeep runs straight at a titanosaur, causing it to stampede through several enclosures, causing the Ornithomimus flock, Phorusrhacos, Elasmotherium, and, worst of all, Matilda the T. rex, to flee through the broken fences and run around freely through the park. Paying no attention to the titanosaur lumbering through her enclosure, Matilda walks right out into freedom, getting the scent of an easy meal. Bob manages to stop the jeep, and the Troodon leaps out and escapes into the undergrowth nearby. Bob runs off to try and capture the escapees. When trying to round up a group of escaped Ornithomimus and the Elasmotherium, Bob is warned that Matilda is on the loose and closing in on him, so he must flee. Matilda then heads for the elephants - she separates the calf from the rest of the herd and quickly runs it to the ground. But Martha, although the herd earlier drove her away, instinctively defends the calf, and with some trumpetings, growls, roars, and waving of tusks, her attack stops Matilda. Nigel then arrives and runs away on foot, trying to lure Matilda away to follow him. Matilda, seeing the prospect of an easy meal, turns away from Martha and starts chasing Nigel. Nigel runs past the Nile crocodile pond, across an open area, and along a jeep track past the Deinosuchus lake, with Matilda closing the gap behind him. The Deinosuchus, accustomed to fighting giant theropods, surges out of the lake at Matilda, who swings around just in time to dodge the attack. This delay buys time for Nigel, who runs into the Time Portal's entry stockaded enclosure and climbs out of it by a ladder. Matilda's jaws are only about a foot distance from one of his feet as he climbs to safety. Nigel shuts the enclosure and Matilda is contained. A few weeks later, extra keepers have been hired. The escaped animals are back in their enclosures. Bob catches the Troodon in a long tunnel trap with droppable doors at both ends, and presumably finds somewhere to keep it. The elephants, thankful for the help and rescue, let Martha join them as a full herd member and be an "auntie" to the elephant calf. The Smilodon cubs have been weaned and are eating meat, but they have not grown visible saber teeth yet.
At the end of the episode we see Nigel at his HQ planning his next mission before travelling through the time portal, suggesting that a future series will be made.