As Europe witnesses the dramatic movement of people across its borders, Panorama reporter John Sweeney joins thousands making the journey from the Greek island of Kos to the Austrian border with Hungary. He meets families fleeing conflict and terror in Syria, refugees separated from their loved ones, children, the old and sick being forced to march to safety. Among this tide of humanity, he also finds economic migrants seeking a better life in northern Europe and he asks, with winter on the way, is the crisis about to claim even more lives?