The underground tunnels between Egypt and Gaza are a lifeline for those trapped inside the blockaded Strip, but along with the clothes, furniture and food that make their way through the tunnels, a dangerous drug - Tramadol - is also entering the territory. Tramal, as it is known in Gaza, is a dangerously addictive painkiller which is illegal without a prescription, but an increasing number of Gazans are becoming hooked on it. Uncomfortably Numb talks to some of those addicts, those who are trying to help them and the authorities seeking to crack down on drug abuse.