Why won't Ruth eat crab?

When Ruth was younger, she lived in Suffolk. There was a river right down the road where people would cast their nets for crabs, the only problem was they'd get more than crabs..... they'd get bodies. Once, a customer's son was hauled in. He was murdered, tossed in the water to drown and then eaten by crabs. Ruth said that crabs would eat anything...... and that she'd never eat a crab.