Das Geheimnis der Todesinsel

A group of tourists travel to an island to see its exotic botanicals. There they meet Baron von Weser (played by Cameron Mitchell), a reclusive scientist studying rare horticulture and experimenting with crossbreeding dangerous varieties of plants. One of the Baron's creations is draining the blood of human beings (through a small hole in their cheek) and the tourists are dying one by one.