Walter Sickert was not the infamous serial killer Jack the Ripper. Let's be clear about it straight now. Among other things, he was away for most of 1888 when a succession of working-class women were killed in and around Whitechapel, east London, as the Walker Art Gallery points out in this fascinating trip into this frightening artist's world.

Except, just next to the wall writing stating this, there is a painting titled Jack the Ripper's Bedroom, which depicts the artist's own apartment. Venetian blinds allow in a sliver of light, which animates a pink bedcover, as if the bed is haunted by a phantom of flesh.

Flayed skin is suggested by the creamy pigment.

The artwork was created between 1905 and 1907. Sickert said that his landlord informed him in 1881 that she had rented the apartment to a guy she suspected of being Jack the Ripper.

However, this piece of urban legend hardly explains the artwork. Without delving into conspiracy theories, Sickert's eerie, sensual portrayal of the chamber suggests at the very least that he had a sick, strangely intimate interest in the murders. He creates a hazy enigma in the room: is it a woman's head developing in the shadows?

Perhaps I was seeing things because Sickert's subtle and enigmatic painterly spells had previously perplexed me. He can detect traces of evil in almost any situation.

This perplexing guy, who was born in Munich in 1860, moved to Britain as a kid, and went on to become one of our greatest and strangest artists, emerges more stranger in this superb exhibition. His modernism is hidden in that uncomfortable manner of seeing.

You may believe that Venice is a straightforwardly lovely topic. However, when Sickert first visited in the 1890s, he portrayed it as an architectural mortuary, with sensuous but brutal brushwork that turns its beauty into empty theatrical décor.

John Ruskin, a Victorian art critic, hailed Venice as a living monument to medieval Christianity's communal spirit. Sickert takes the same building and turns it into a monstrosity: a God-forsaken Venice.

He then hired Venetian sex workers to pose in his hotel room for him. One lady, her face twisted and one eye gazing furiously, clings to the bedpost as instructed. She is completely dressed, but she is terrified of forced sexuality.

Sickert's Venice is scary, but his London is sinister. Gilded statues of ancient gods gleam from magnificent architectural fantasias in the music halls he started painting in the 1880s. But we know it's all made of paper.

Sickert came to some bleak conclusions about human beings while painting these Victorian nightlife establishments.

His drawings show how he secretly watched audience members and caricatured them while they laughed or leered. And we know they're keeping an eye on ladies.

Sickert alternates between crowd scenes and young ladies singing on a large empty stage in his drawings and paintings. Minnie Cunningham's bold red outfit and bonnet are captured in his 1892 picture, but her face is buried by the darkness. Her features are shown in close-up in the sketches, and she seems to be unhappy.

The masculine audience is subjected to Sickert's skepticism. A bowler-hatted throng watches an apparently exciting performance in his painting Gallery of the Old Bedford, painted in 1894-5.

They balance like ecstatic monkeys, dangling from the top balcony's front, their faces hidden by meaty masks. The expressions in another scenario are even more monstrously disordered.

Sickert's images of London nightlife are inspired by the café paintings of the French impressionists, particularly Degas, who is one of his favorites. Their paintings look for beauty in everyday life.

Even when Degas depicts a lonely absinthe user, she is attractive, and he admires the absinthe's green color. In the English music hall, Sickert finds something really terrible - a barely controlled, violent eroticism.

In 1900, London was the wealthiest and most powerful city on the planet, at the heart of a global empire. It's a Darwinian cesspool for Sickert. Men are just a few generations removed from apes. They stare moronically at a woman they want to snag and crush.

That leads us to his nudes. Sickert began painting women nude in cheap London apartments about the time he painted Jack the Ripper's Bedroom. The criminal element persisted.

Emily Dimmock was assassinated in Camden Town in 1907, allegedly by a customer. Sickert had just relocated to the neighborhood and began painting nudes in 1908 that clearly alluded to the murder.

What Shall We Do to Pay the Rent? The Camden Town Murder, or What Shall We Do to Pay the Rent? depicts a guy sitting close to what seems to be a woman's dead corpse. The artist himself is equating voyeurism and violence, painting and murder, with some trepidation.

Sickert's other tones in Camden bedrooms are as unsettling. Mornington Crescent Nude, dated 1907, shows a lady waiting on a bed through an open door. In the light filtered by a blind, we see her breasts and hips, but her face is obscured, and her expression is unreadable.

La Hollandaise, painted in 1906, has her legs in front of us and her breasts on display, but her face is again obscured — in fact, her nose is missing. As if it were a skull.

Sickert's tight and stressful paintings - the wild nighttime throng and unsettling nudes – are at the center of the Walker's fantastic show. To comprehend him, one must go beyond the elegant drawing rooms of Victorian and Edwardian British art to the broader reality of his period.

Sigmund Freud, a Viennese contemporary, viewed civilization as a thin covering over humanity's sexual urges and obsessions. Sickert's paintings of music halls make a similar statement.

His nudes go into his own mind. He does this not just to shock, but also to liberate art from deception.

These aren't nice works; they're filthy admissions. Walter Sickert's modernism isn't beautiful. But that's life.

Thanks to Jonathan Jones at The Guardian whose reporting provided the original basis for this story.