John Agar pretty much set the tone for the sci-fi heroes in the 50s and 60s. Either he was stopping the monster, being the monster or being possessed by the monster and then helping stop the monster. This is the third category, and he gets help from a good alien presence as well, who possesses his dog for good measure.
It's a rare thing back then to see a good alien helping to defeat the evil alien. I like that this shows both sides. It's not a great movie, but it's fun and memorable.