Castle Full of Blackbirds continues the story of Sara May Blackburn, the fan-favorite character from Hellboy and the B.P.R.D.: The Return of Effie Kolb. When Sara May headed for New York after the events of The Return of Effie Kolb, she had one goal in mind: find the mysterious Miss Brook at the Linton School for Girls, and ask her what she knows about the mysterious powers that have plagued Sara May her whole life. But as is often the case with these things, the answers are not as simple as all that. Sara May is in for an education in more than just reading, writing, and 'rithmetic at the Linton School.