A young man struggles to access sublimated childhood memories. He finds a technique that allows him to travel back into the past, to occupy his childhood body and change history. However, he soon finds that every change he makes has unexpected consequences.
In the final days of World War II, the Nazis attempt to use black magic to aid their dying cause. The Allies raid the camp where the ceremony is taking place, but not before they summon a baby demon who is rescued by Allied forces and dubbed "Hellboy". Sixty years later, Hellboy serves the cause of good rather than evil as an agent in the Bureau of Paranormal Research & Defense, along with Abe Sapien - a merman with psychic powers, and Liz Sherman - a woman with pyrokinesis, protecting America against dark forces.
When the Mystery Inc. gang is invited to Spooky Island, a popular amusement park, they soon discover that the attractions aren't the only things that are spooky. Strange things are happening, and it's up to Scooby, Shaggy, Fred, Daphne, and Velma to uncover the truth behind the mysterious happenings.
