The Budapest subway system, the world's second oldest, is a dark, labyrinthine netherworld as vast and various as the city above it. Of the hordes of people who can be found there, most are passing through on their ways to better, brighter places. But, there are those who spend most of their lives underground--the beleaguered ticket inspectors or "controllers," who are assigned in teams to various sections of the system, and whose thankless job it is to ensure that no passengers ride without paying. Bulcsu, the defacto leader of one such inspection squad, is in his late twenties. Working with an eclectic and especially disheveled bunch, Bulcsu is assigned to the least savory and safe area of the underground. Sequestered in subterranean squalor, these men find that night has become indistinguishable from day and that living has become almost indistinguishable from dying. Most of the inspectors live this way without care or question. But Bulcsu is clearly a breed apart. No one knows much of anything about him or his way of life away from the job. From time to time he runs into someone he used to know from above ground. When this happens, Bulcsu either avoids contact or lies about his current occupation. Then, in the wee hours of the morning, when his shift is over, he finds a secluded platform far away from everyone and everything and goes to sleep. Bulcsu and his mates do their job, albeit halfheartedly, and inspect tickets. A rival group of inspectors, all slick and polished, compete with them for better placement and perks. Bulcsu and his cronies cannot compete on the job, but find ways to get even after hours. Then, as always, there appears a beautiful, mysterious young woman, Sofie with whom Bulcsu falls instantly in love. And, as always, there is danger--here, in the form of a shadowy killer who appears out of nowhere and pushes unsuspecting passengers under the relentless wheels of oncoming trains. Because Bulcsu never goes home, he becomes a suspect in these slayings. Having fallen for Sofie, Bulcsu finds that life once again has meaning. But, with the authorities and a killer at his heels, there is only one way out: he himself must apprehend the man in the shadows, the demon who haunts this underworld.