Good guys cause an innocent victim's murder
The victim is Professor Meikeljohn, the elderly scientist with the umbrella. If Lugosi and Co. already know that Karloff killed one random guy to fake his own death so even if it's them his target he's not above killing innocents for his purposes, they should know better than give a meeting they intend to attract Karloff to, and then make it INVITATION ONLY. It should be expected by them that Karloff would kill one of the guests to impersonate him and enter, right?
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