Plants' solutions to life's challenges are as ingenious and manipulative as any animal's. Innovative time-lapse photography opens up a parallel world where plants act like fly-paper, or spring-loaded traps, to catch insects. Vines develop suckers and claws to haul themselves into the rainforest canopy. Every peculiar shape proves to have a clever purpose. The dragon's blood tree is like an upturned umbrella to capture mist and shade its roots. The seed of a Bornean tree has wings so aerodynamic they inspired the design of early gliders. The barrel-shaped desert rose is full of water. The heliconia plant even enslaves a humming bird and turns it into an addict for its nectar.

It is a nightmare that has stalked us for centuries: hordes of human beings transformed into mindless, cannibalistic monsters. Could this civilization-ending nightmare become reality? Scientists have discovered pathogens that turn insects into the walking dead. New strains of viruses are attacking humans every day. Mathematicians have calculated the likelihood of surviving a zombie virus outbreak: they’re not hopeful. Now neuroscientists are discovering how easy it is for us to lose conscious control of our bodies. Are we at risk of becoming puppets? If we were in the middle of a zombie apocalypse, would we even know it?

The third episode is devoted to the ways in which plants reproduce. Pollen and a stigma are the two components needed for fertilisation. Most plants carry both these within their flowers and rely on animals to transport the pollen from one to the stigma of another. To do this, they attract their couriers with colour, scent and nectar. It isn't just birds that help pollination: some mammals and reptiles also do so. However, it is mostly insects that are recruited to carry out the task. To ensure that pollen is not wasted by being delivered to the wrong flower, some species of plant have developed exclusive relationships with their visitors, and the gentian and its attendant carpenter bees is one example. Since pollen can be expensive to produce in terms of calories, some plants, such as orchids, ration it by means of pollinia and a strategically placed landing platform. Other orchids offer no reward for pollination, but instead mislead their guests by mimicking their markings and aroma, thus enticing males to 'mate' with them (Pseudocopulation). The most extreme fertilisation method is one of imprisonment, and one plant that uses it is the dead horse arum. It is often found near gull colonies, and mimics the appearance and smell of rotting flesh. Blow-flies are attracted to it, and are forced to stay the night before being allowed to depart in the morning, laden with pollen. Finally, Attenborough introduces the world's largest inflorescence: that of the titan arum.

Bladderwort utricularia is a pond-dweller that is among the fastest known, its traps snapping shut in less than a millisecond. As the seasons change, David demonstrates how plants operate on a different time scale to us; how they modify their lives according to the time of year. We discover insects’ hidden links with plants, both as pests and pollinators. UV-sensitive 3D cameras reveal the invisible alter-ego of plants and their flowers’ mesmerizing patterns; a parallel-dimension of strange colours and stunning patterns through which plants communicate with them. With the aid of visual effects, David steps among the swirling vortices of plant scent; communication signals with which plants are inextricably plugged in to the natural world. And using a tuning fork, he demonstrates how plants and insects can even communicate with music. As autumn envelopes the Gardens, fungi reveal themselves not as the enemies of plants but their vital allies. In Kew’s atmospheric Fungarium, David discovers a specimen that has the power of mind control and another that lives underground where it has grown to be so big it can be counted as the largest single organism on the planet. It is 6 times bigger than Kew Gardens itself.

Invertebrates don't always operate alone. True society was the last feature to evolve in invertebrates, as recently as the time of Tyrannosaurus. In the last programme see the tensions below the surface in some of the great social structures built by insects, and witness the carnage when an ant colony and a termite colony wage war.

About 340 million years ago a brand new family of animals was evolving in the primeval swamps. They were to go one step further than the amphibians who had emerged onto dry and before them. For they would eventually completely cut their ties with water. They were the ancestors of todays lizards. They evolved scaly impermeable skins and moved up into the forests. They diversified into a multitude of different shapes and sizes. They developed signalling systems to communicate with one another. And they squabbled as animals do. For food they hunted insects that were already well established on the land in great numbers. And here without returning to water they produced their families. They powered their bodies not only with food but with the heat that they drew directly from the sun.
As they diversified so they spread into the harshest of the lands habitats. The baking waterless deserts which eventually they would come to dominate. Discover jacky lizards that wave, wrestling beaded lizards and the the world's smallest chameleon, which is no bigger than his thumbnail, and the biggest lizard in Australia.