Factual error: As Frederick is explaining to his guests how to use their .45 automatics, he fires one round at a near-by vase, shattering it. However, it leaves no bullet hole in the wall directly behind the vase.
Factual error: After his wife falls into the pit, Frederick casually grabs Dr. Trent's skeleton; the skeleton that only moments earlier had been submerged in acid. His hand should have been badly burned.
Factual error: In reference to the skeleton in the pit, a skeleton with its flesh burned away would have nothing to hold it together. Frederick states it is Dr. Trent's skeleton. For him to run wire through the skeleton would have been impossible in the time he had. He had only a few minutes at best before his wife came down. He'd have had to fish the loose bones out of the pit, wire them all together, attach the whole thing to the puppeteer rig, and put it back in the pit.