Every so often we hear on the evening news that a firebug has set fire to a building, destroying property and endangering lives. Usually, however, most of the intended victims managed to escape because they heeded the sound of fire alarms or the shouts of their neighbors. But suppose for a moment that a more calculating pyromaniac were to dress himself in a business suit and calmly knock at each door in a hotel or apartment building, warning the residents to “Please, remain inside your unit, because