The cry for help, a neatly folded letter stuffed inside a package of Halloween decorations sold at Kmart, traveled 5,000 miles from China into the hands of a mother of two in Oregon. Scrawling in wobbly English on a sheet of onionskin paper, the writer said he was imprisoned at a labor camp in this northeastern Chinese town, where he said inmates toiled seven days a week, their 15-hour days haunted by sadistic guards.