This is based on the book of poems of the same name by Anne Sexton. An American mental patient, she wrote as a form of therapy. Gabriel was impressed that she wrote entirely for herself rather than an audience.
Sexton made five suicide attempts, the fifth being successful: she died of carbon monoxide poisoning in 1974.
The title came from Anne Sexton’s 1969 play 45 Mercy Street. She was also working on a poem with the same title at the time of her death.
Gabriel could relate to Sexton as a deep thinker with a troubling depression who searches for meaning through her art. He used the image of darkness on Mercy Street to signal her depression.