Blood-red walls, a sour green ceiling, four lamps buzzing with yellow halos and a few lonely drinkers. Van Gogh stayed awake three nights to paint The Night Café in Arles, and wanted it to feel like a place where you could go mad.

A god eating his child on the wall of a dining room, a severed head painted on a parade shield, skeletons tending a garden: eight paintings that have unsettled viewers for centuries, and what their painters meant by them.

Edvard Munch walked along a path above the Oslofjord one evening in January 1892. The sun was setting. The clouds, he wrote in his diary, turned 'blood-red.' His two companions kept walking. Munch stopped at the railing, exhausted, and felt 'an infinite scream passing through nature.' He painted that moment four times between 1893 and 1910. The first painted version is the one the world knows. The Scream is, after the Mona Lisa, the most reproduced painting in Western art. Mo