I've been on a vintage Columbia cheapie phase of late. Watched Face Behind the Mask and The Devil Commands.
I'd never seen the Peter Lorre film before. It's an effective noir-ish item with horror overtones. The plot has loopholes you could drive a truck through, but Lorre's performance (especially considering he's having to restrict his facial expressions to give the impression he's wearing a rubber mask) makes it worthwhile.
The Karloff film is a much better concept than a movie. It's a pretty lousy script, but he gives a good sympathetic performance. There's a couple of creepy moments, as when all the corpses gathered around the table (what did he need them for, anyway? It's never explained) are pulled forward by the electro vortex of Boris's contraption. Overall ho-hum, but at 60+ minutes it's not a chore to get through.