Prawn, or shrimp if you're American, was once a luxury and now it's an everyday pleasure. Cheap for us to buy, the human cost of their production is unbelievable. This is the story of globalized slavery and how giant international supermarkets like Walmart, Tesco, Carrefour, Morrisons and Iceland are selling shrimps fed by slave labor.

Thai fishing industry is rife with abuse, torture and summary executions. Thailand is the world's largest supplier of shrimps. The six-month Guardian investigation has traced the complex food chain from the boat to the supermarket shelf, proving for the first time that the low price of the shrimps on your plate depends on slave labor.

Late at night a cargo boat slips into one of Thailand's busiest ports. On board is a man who hasn't seen land in over 18 months. Like many Thai ports this is a hub for human trafficking where international network of slave traders often buy and sell migrants onto Thailand's illegal fishing boats... and he isn't safe.

The last time he was back on land he was tricked and sold onto another boat. This time his freedom has been bought by a local charity for just £450. Terrified and confused and unaware that he is free he fears that he's about to be trafficked again. Even free he's still afraid to show his face on camera.

A former monk from Cambodia was also a part of the invisible migrant workforce that props up Thailand's multi-billion-dollar shrimp industry. Each year thousands of migrants pay brokers large sums of money to smuggle them into Thailand in search of a better life. With his parents struggling to feed six children he left Burma to help provide for his siblings. After his mother died he was abandoned by his father. He lived as a pagoda boy until he left rural Burma as a teenager.