The two men first met thirteen years ago.
Manfred Lütz had invited Otto Kernberg to give a lecture in Cologne.
Kernberg, then 79 years old, took Lütz through a museum that he had never visited before and stayed afterwards for dinner.
From then on he came to Cologne every two years for a gig and hours of talks with Lütz.
This January, Lütz traveled to Kernberg in New York, and this time the talks should turn into a book.
On the first day, a Friday, the psychiatrists spoke to each other for five hours.
Then eight hours on Saturday and nine hours on Sunday.
Kernberg, now 92, had to go back to work on Monday, with a twelve-hour day ahead of him.
With beaming eyes he assured Lütz that he didn't mind, he loved his work.
Manfred Lütz:
What is the art of a good partnership?
Otto Kernberg:
You have to develop a good relationship in the three main areas.