Goofs

The helicopter that is shown flying throughout most of the film has the registration G-AWFY, but a different one that had been stripped for scrapping was used in it for the one catching fire and exploding and it can be seen that it has the registration T-AWEK.

When Foote asks Tom if it is a picnic lunch he is carrying in the bag, Tom's position clearly does not match the one shown in the previous scene where they are talking about the cameras and looks more close to the position that he had when he approached him.

Right before Tom makes everyone do the test with the silver bullet, Davina is talking about how they already had the test with the silver candlestick and looking to the side, but in the very next scene, she is looking straight ahead.

When Tom finally confronts the werewolf it is shown in the darkness of the forest, but then in another scene it is shown outside of the forest, where it is light.

A truly awful use of "day for night" scenes in this film make it painfully obvious that the "night" scenes in it were done during the day.

Tom fires far more rounds from his Rexim-Favor Mk5 sub-machine gun that can be held in its 20-round magazine, although he is shown reloading once.

When Tom works the bolt on his rifle after firing his last shot at the werewolf, no shell casing is ejected from the gun.

Tom Newcliffe invites several people to his estate because he is convinced that one of them is a werewolf and he intends to identify and hunt the one who is. After dinner the first evening, he explains this to the gathered people. Newcliffe goes from one guest to the next, explaining how he suspects each of being a werewolf, but he does NOT indicate that he has conclusively (or at least to his satisfaction) confirmed the existence of one werewolf and determined that its normal human form must be one of his invitees, but instead outlines evidence that each person, independently of the others, might be a werewolf. Given the existence of such creatures, Newcliffe has presented a situation in which anywhere from none to all of his special guests might be werewolves rather than one, no more and no less.

When the alarm shows that the werewolf has left the estate and is prowling in the forest, Tom has his surveillance expert help him track the beast. He could have taken a few seconds to look in on all the guests via the spy cameras to see which one was missing from their room and so discover the werewolf's identity, but this does not seem to even occur to him.

Dr. Lundgren states that all are safe because wolf's bane ("Acontium") doe not grow in Great Britain. This is false, as it is a native species to that country and has been both documented since the first century A.D. and cultivated before 1600.

When the werewolf flees the house Tom comments that he has one silver bullet left in his gun, which will make things sporting, but a few minutes earlier he had given each of his surviving guests a silver bullet while testing to see if they reacted to the silver. Had he thought to get these bullets back before chasing the werewolf, he could have had most of a full clip, but this does not seem to even occur to him.