This week, we begin with a disturbing medical mystery. Since the start of the year, almost 200 children worldwide have fallen ill with hepatitis—or liver inflammation—without any apparent cause. Most of the children are under five, and nearly half of the cases were in the UK. Vic Gill asks clinical epidemiologist Deepti Gurdasani, Queen Mary University of London, what we do and don't know about these rare cases. Also on the programme, with a huge tidal range, Wales and the west coast of England have become the focal point for a new generation of tidal power plans. So, is the tidal energy revolution finally happening? Roger Falconer, Emeritus Professor of Water and Environmental Engineering at Cardiff University, and Andrew Scott, CEO of Orbital Marine Power, which has demonstrated a working tidal stream turbine - called O2 - off Orkney, share their insights. And fancy eating an insect burger? Or how about adding seaweed smoothies or mycoprotein meatballs to your diet? Fellow BBC science correspondent Helen Briggs shares how lab-grown proteins could make our diets much kinder to the planet. And a recent study has found that a fifth of reptile species are at risk of extinction. Conservation scientist and study co-author Monika Bohm, Indianapolis Zoo in the US, tells us how, despite the gloomy findings, she remains hopeful. Presented by Victoria Gill Produced by Alex Mansfield and Samara Linton