One morning in May 1993, a man living outside Chicago, Illinois, stepped out onto his front porch – and froze. There was a shoebox sitting there, with a note that said “To Sandra” – but no one named ‘Sandra’ lived at his house. The man’s heart started to race. There was a bomber on the loose, and the whole city was on edge – so he called 911. The box on his porch would turn out to be nothing, but until the bomber was found, nobody knew what the next box would contain.