For 54 years, Mike and Mina Block made marriage look easy. Then, three months after Mina died suddenly of pneumonia, Mike moved in with Kitty, his former secretary—and married her. Stunned, son Doug Block set out to investigate what he had for so long taken for granted. The resulting documentary begins shakily, with a naked self-consciousness that can be off-putting, but quickly develops into an absorbing and ever deepening drama. Essentially the story of how a fiftysomething son loses his innocence by finally coming to know his parents, 51 Birch Street finds its most compelling material in Mina’s journals, 30 years of emotional self-examination, which broadside Block with revelations. His struggles over their content are also engaging, as, finally, are Mike’s questions for Doug. When the father turns the lens on the son, asking him to evaluate his own marriage, Doug’s hesitation is rich.Is the son any happier than the father?