three child be bear at the exact same time and during a lunar eclipse . just before their 10th birthday they embark on a killing spree . bloody birthday be a typical slasher from early 80 . it a pretty average stuff with plenty of nudity . the evil child never generate any menace and there be almost no suspense . there be also no gore or scare in bloody birthday and but the film be mildly entertaining . unfortunately no real explanation be provide for the kid sudden homicidal mania . the murder scene be quite gruesome for example we have get death by handgun and baseball bat and skip rope and shovel . so if youre a fan of early 80 slasher movie give this one a look .