Dr Chris and Dr Xand turn back the clock and look at what medicine was like in the First World War. They meet a Paralympian runner who swaps her awesome blade for a World War I leather leg, and they look at the little critters that infested the trenches. Then they set up a massive experiment to demonstrate how soldiers' bodies had to cope with the pressures exerted by huge explosions.

Dr Chris and Dr Xand show you an awesome body trick to amaze your friends with, and reveal another way your brilliant body heals itself if you get injured. The doctors also look at some of their best bits of Operation Ouch! so far.

The doctors show that your breath is just as unique as your fingerprints, and Dr Chris goes behind the scenes of medical drama Casualty to see how they make fake body parts look so realistic. Meanwhile, over in accident and emergency, one patient has a nasty infection on his cheek and another has something stuck in his ear!

The doctors use real stomach acid to do an experiment to reveal how the digestion process starts. Also, Dr Chris proves that the younger you are, the more sounds you can hear. Meanwhile, over in accident and emergency, one patient has broken his arm tripping on a kerb and another has banged his head on the handlebars of his bike.

The doctors prove that we all have invisible ink inside our bodies, and Dr Xand sees head lice removed from someone's hair with a vacuum cleaner. Meanwhile, over in accident and emergency, one patient has banged her head on a telegraph pole and another has a piece of crayon in her ear...

The doctors look at the awesome work that goes on inside the liver, and Dr Chris extracts snot from members of the public for a very useful experiment. Meanwhile, over in A&E, one patient has a massive lip from an allergic reaction and another has surgery to repair his broken nose.

The doctors take a closer look inside their ears to prove how earwax has a really important job to do, and Dr Xand meets a pioneering professor who makes body parts. Meanwhile, over in accident and emergency, one patient has injured her toe and another has swallowed a hair clip...

Dr Chris uses a tiny camera to reveal what happens in his throat when he swallows food, and Dr Xand enters a special chamber that removes sensory data from his brain. Meanwhile, over in accident and emergency, one patient has a broken ankle and another has split her earlobe.

The doctors take a close-up look at how the eye works, and Dr Chris finds out what body fat does by looking at some of his own under a microscope. Meanwhile, over in accident and emergency, one patient has a mystery rash and another has a bad infection under her fingernail.

The doctors meet Larry the vomiting robot to show the power of puke, and Dr Xand goes on an urgent mission on a motorbike to deliver blood to a hospital. Meanwhile, over in accident and emergency, one patient has fallen off his bike and another has a football injury...

The doctors reveal what lurks inside the plaque on your teeth, Dr Chris uses a remote-controlled car powered by his own wee, and Dr Xand decides to get his verruca treated. Meanwhile, over in accident and emergency one patient has some grit in her chin and another has a screw stuck up his nose.