Dr. Stefan Donat, a doctor from Frankfurt, unexpectedly becomes the sole heir to his wife Agnes' estate after she dies of a terminal illness, even though they had been divorced for years. The change in the will in Stefan's favor was made on the day Agnes died in her apartment between 4 and 6 pm. The original heiress, Mingo Fabian, contested the will. She is 23 years old, Agnes' cousin and was also friends with Stefan Donat. She finds this step very difficult, but her lawyer, Dr. Bernburger, persuades her to take it, as he wants to marry her. The body is exhumed and shortly afterwards Dr. Donat is arrested on suspicion of murder...