Doctors, twins and part-time aid workers Chris and Xand van Tulleken want to see for themselves what conditions are like for migrants fleeing through Europe at the height of winter. They travel to Lesbos in Greece, through the Balkans and on to Berlin and Calais, spending time with medics, charities and volunteers in camps and clinics to explore what is being done on a medical and humanitarian level in response to the current refugee crisis.