Behind the scenes at Six Flags’ new 4D free-fly coaster The Joker

GURNEE, Ill. -- A new rollercoaster is coming soon to Six Flags Great America and thrill seekers are in for a twisted ride.

WGN's roller coaster enthusiast Marcus Leshock got a behind-the-scenes look at the construction of the park's new 4D free-fly coaster called The Joker.

Six Flags opens April 29, and The Joker should be ready to ride by Memorial Day weekend.