Horizon discovers what your cat really gets up to when it leaves the cat flap. In a groundbreaking experiment, 50 cats from a village in Surrey are tagged with GPS collars and their every movement is recorded, day and night, as they hunt in our backyards and patrol the garden fences and hedgerows. Cats are fitted with specially developed cat-cams which reveal their unique view of our world. You may think you understand your pet, but their secret life is more surprising than we thought.

Documentary-maker David Malone delves into the secrets of ocean waves. In an elegant and original film he finds that waves are not made of water, that some waves travel sideways and that the sound of the ocean comes not from water but from bubbles. Waves are not only beautiful but also profoundly important, and there is a surprising connection between the life cycle of waves and the life of human beings.

Dr George McGavin and Dr Zoe Laughlin set up base camp at one of the UK's biggest sewage works to investigate the revolutionary science finding vital renewable resources and undiscovered life in human waste.
Teaming up with world-class scientists, they search for biological entities in sewage with potentially lifesaving medical properties, find out how pee can generate electricity, how gas from poo can fuel a car and how nutrients in waste can help solve the soil crisis. They follow each stage of the sewage treatment process, revealing what the stuff we flush can tell us about how we live today, and the mind boggling biotechnology being harnessed to clean it, making the wastewater safe enough to return to the environment.

It's a timeless classic of children's literature and the third most-quoted book in English after the Bible and Shakespeare. But what lies behind the extraordinary appeal of Alice's Adventures in Wonderland to generations of adults and children alike? To mark the 150th anniversary of its publication, this documentary explores the life and imagination of the man who wrote it, the Reverend Charles Dodgson, better known as Lewis Carroll." Broadcaster and journalist Martha Kearney delves into the biographies of both Carroll himself and of the young girl, Alice Liddell, who inspired his most famous creation. Kearney's lifelong passion for Carroll's work began as a young girl, when she starred as Carroll's heroine Alice in her local village play. She discusses the book with a range of experts, biographers and distinguished cultural figures - from the actor Richard E Grant to children's author Philip Pullman - and explores with them the mystery of how a retiring, buttoned-up and meticulous mathematics don, who spent almost his entire life within the cloistered confines of Christ Church Oxford, was able to capture the world of childhood in such a captivating way

Silk is the invertebrates' great invention, used in a range of ways from from the protective stalks of lacewing eggs to the amazing hanging threads of New Zealand's 'glow worms'. Spiders, though, have taken silk-spinning to extremes. The common wolf spider has no web, but the female is a gentle parent, encasing her eggs in silk and carrying the precious bundle wherever she goes. The bolas spider uses a ball of sticky silk soaked in a copy of moth pheromone to lure its prey. Millions of communal spiders live and feed together in a vast, towering web - an arachnophobe's nightmare.

Fourth episode examines how plants either share environments harmoniously or compete for dominance within them. Attenborough highlights the 1987 hurricane and the devastation it caused. However, for some species, it was that opportunity for which they had lain dormant for many years. The space left by uprooted trees is soon filled by others who move relatively swiftly towards the light. The oak is one of the strongest and longest-lived, and other, lesser plants nearby must wait until the spring to flourish before the light above is extinguished by leaves. Tropical forests are green throughout the year, so brute force is needed for a successful climb to the top of the canopy: the rattan is an example that has the longest stem of any plant. As its name suggests, the strangler fig 'throttles' its host by growing around it and cutting off essential water and light. Some can take advantage of a fallen tree by setting down roots on the now horizontal trunk and getting nutriment from the surrounding moss and the fungi on the dead bark. The mountain ash (eucalyptus regnans) grows so tall, that regeneration becomes a considerable problem. It is easily flammable, so its solution is to shed its seeds during a forest fire and sacrifice itself. It therefore relies on the periodic near-destruction of its surroundings in order to survive. Attenborough observes that catastrophes such as fire and drought, while initially detrimental to wildlife, eventually allow for deserted habitats to be reborn.