In forests across the planet, secretive hunters are searching for that rare and insanely expensive wild delicacy: the truffle. The organism, which grows underground, tethered to tree roots, can fetch thousands of dollars per pound from upscale restaurateurs. The only way to find these particular fungi are dogs specially trained to sniff them out. Not surprisingly, the truffle business is not unlike the illegal-drug business, with lots of sneaking around in the night and powerful characters vying for control over markets. Outside contributing editor Rowan Jacobsen took a journey deep into the underworld of truffle hunters )that began in the in the ancient forests of Europe and ended up, very unexpectedly, in the hills of Appalachia.