Tristan and Vanessa are on the Pacific coast of Costa Rica in search of the largest collection of turtles in the world. Up to 150,000 turtles come to this area for a mass nesting, known as the "arribada," in which they lay their eggs on a 1-kilometer stretch of beach. Timing is everything; by consulting local fishermen who harvest the turtle eggs, tide timetables and the moon, Vanessa tries to pinpoint the critical moment when the turtles will arrive. Once Tristan and Vanessa are on location, it’s just a matter of waiting and hoping that their timing is correct!

But in this part of the world, plenty is happening. Walking along deserted beaches, through steaming mangrove swamps and beautiful coastal forests, the pair discovers lizards that can literally run on water; troops of capuchin monkeys using tools to open clams; and vast swarms of army ants devouring anything in their paths.

Vanessa’s turtle timing is impeccable; on the fifth day, Tristan and Vanessa witness the first of these prehistoric animals hauling itself out of the surf and up the beach to lay its eggs. For both Tristan and Vanessa, it’s a huge relief to see these first turtles in what turns out to be one of the biggest arribadas on record! Now their work really starts: the pair must capture on film these rare and endangered animals in their struggle to breed and survive the next generation.