During a visit to Ruth von Kleist-Retzow, the Prussian patroness of Bonhoeffer’s covert seminary work, Bonhoeffer met her granddaughter, Maria von Wedemeyer, for the first time since she was 12. Bonhoeffer had long maintained pastoral contacts with the family and had not been looking for a romantic relationship, but he was struck by Maria’s intelligence and passion.

Over the following months, Maria's family faced the tragic loss of her father and brother, so Bonhoeffer made no rapid attempts to strike up a further connection with Maria, but instead spent time seeking God’s guidance. Maria was many years his junior, and he was increasingly involved in dangerous, life-threatening work, both of which weighed against beginning a romance. Around the same time, however, Maria’s grandmother Ruth was hospitalized for an illness. Bonhoeffer and Maria’s visits often overlapped, prompting Ruth to notice the growing connection between them and encouraging their interactions. However, Maria's mother grew concerned that things were progressing too quickly and took steps to intervene.

Initially surprised by the notion of a romantic relationship, Maria eventually embraced her feelings for Bonhoeffer, who reciprocated. They moved slowly, taking periods apart to think and pray and make room for her mother’s reservations, but in the end they decided to get engaged.