The story begins when wins a mysterious golden cracker in a lottery. When he tries to open it, it releases a strange vapor that turns him into a vain, arrogant, and power-hungry figure. He proclaims himself "Emperor Lambik I" and starts causing chaos.

De Keizerkraker is a later-era Suske en Wiske story (post-Vandersteen, written by Marc Verhaegen or a studio writer), known for its playful mix of history and fantasy, and a slightly more modern dialogue style than the classic 1950s–70s albums.

The group must travel back in time to the Roman Empire to find out how the original emperor was defeated, and obtain the — a second cracker that can neutralize the first. Along the way, they face Roman soldiers, gladiator fights, and the ghost or lingering influence of the mad emperor.

(with Tante Sidonia and Professor Barabas in supporting roles) try to stop him. They discover that the cracker is actually an ancient artifact that once belonged to a real (fictional) Roman emperor, Keizer Krikkebij (Emperor Crackerjack), who used it to seize absolute power.