Surprisingly, Universal Studio waited seven years to release this sequel which is nearly as great as the original. The Invisible Man Returns is a classic horror at its best. First, it starts with a great screenplay whose writers include director Joe May and Curt Siodmak who also wrote The Wolfman (1941), Frankenstein Meets the Wolfman (1943) and House of Frankenstein (1944) among others. The story works well and begins with the owner of a coal mining operation, Geoffrey Radcliffe, who has been falsely imprisoned for the murder of his brother and is scheduled to be hanged. He is given the serum to make him invisible by Dr. Frank Griffin who is the brother of the original Invisible Man. He then sets out on a quest to find the true murder while battling his descent into madness. Great stuff!!!
The second thing this movie has going for it is a great cast. Vincent Prince is great as Geoffrey Radcliffe. He fills Claude Rains shoes rather well as the Invisible Man which is a challenging role since we never see Price's face on screen until the end of the film. His expressive voice is the perfect choice for this role. The Invisible Man returns also includes great performances by Cedric Hardwicke [The Ghoul, The Ghost of Frankenstein] as detective Richard Cobb and John Sutton [Return of the Fly, The Bat] as the Dr. Griffin.
Finally, the special effects are really excellent considering the time period of the film. They did more this time out than they did in the original film and filled the movie with lots of visual delights. You simply can't go wrong with watching this one. It's classic Universal Horror at its best and is a joy to watch form start to finish.
For more info check out the film's entry in IMDB.