This one is an art episode, but also a murder episode and also a madness episode. Artist Richard Dadd's life story is quite sad, but his art remained consistently good, even at the lowest points in his life.
Research:

SYMHC Classics: Gustave Courbet
40:51

Behind the Scenes Minis: Oh, Kropotkin!
17:28

Peter Kropotkin's Mutual Aid, Part 2
49:57