On entering the show at the Royal Museum of Fine Arts, you’re confronted with a line from Victor Hugo’s Cromwell: “The grotesque will play the role of the beast in man”. A taste of things to come.

All three artists were each in his own right pioneers of modern art. Goya portrayed inner turmoil and the horror of his era, Redon became one of the leading symbolists with his bizarre and fantastical drawings, and Ensor, slowly but surely, banished all realism from his colourful and very expressive paintings.

The influence of Goya, a former 18th-century Spanish court painter, on the 19th century Redon and Ensor was immense. They were inspired by his morbid and absurd combinations of demons, devils and anguish. An entire room is dedicated to his sinister etchings of human Folly, where Goya portrays the darker side of human nature in all its shapes and sizes, often covered up with masks – a notion that was revived in Ensor's later work.

The exhibition alternates light rooms with darker ones, suggesting that you are entering the belly of the beast. Redon figures heavily in the darker, more intimate spaces. The French painter and printmaker’s work is simple yet symbolic, melancholy yet surreal. The morbid constructions enhance the monster-filled dream world of this mad genius – a place both brutal and surprisingly peaceful.

Finally, our own Belgian Ensor, whose love for bright colours and masks have made him legendary. Not only masks but also faces are hidden in the most surprising places in his drawings and vivid paintings. He sought to emphasise the ornamental aspect of the grotesque, literally masking the hidden truths of humanity. Together with Redon, he is also responsible for the highlight of the exhibition, a series of disquieting drawings inspired by the works of Edgar Allen Poe.

The Museum of Fine Arts, which already holds the majority of Ensor’s work, gathered many of the other paintings, drawings and prints from around the globe. Goya, Redon, Ensor is an ideal run up to the 2010 Ensor Year.