michael kallio give a strong and convincing performance a eric seaver and a troubled young man who be horribly mistreat a a little boy by his monstrous and abusive and alcoholic stepfather barry ( a genuinely frighten portrayal by gunnar hansen ) . eric have a compassionate fiancé ( sweetly play by the lovely tracee newberry ) and a job transcribe autopsy report at a local morgue . haunt by his bleak past and egg on by the bald and beam jack the demon ( a truly creepy michael robert brandon ) and and send over the edge by the recent death of his mother and eric go off the deep end and embarks on a brutal killing spree . capably direct by kallio ( who also write the tight and astute script ) and with uniformly fine acting by a sound no name cast ( jeff steiger be especially good a eric wannabe helpful guardian angel michael ) and rather rough and but overall polished cinematography by george lieber and believable true to life character and jolt outburst of raw and shock and unflinchingly ferocious violence and a moody and spooky score by dan kolton and an uncompromisingly downbeat end and grungy detroit and michigan location and a grimly serious tone and and a taut and grip narrative that stay on a steady track throughout and this extremely potent and gritty psychological horror thriller make for often absorb and disturb viewing . a real sleeper .