Van der Valk

Why would German Wolf Gebhadrt decide, in middle age, to take up an apprenticeship in stonemasonry in Amsterdam? Why would a man killed in a car accident be carrying a newspaper cutting with a photo of Gebhardt? Van der Valk senses that Gebhardt is in danger and even attempts to have him taken into protective custody when he refuses to co-operate with inquiries. Short on options, van der Valk makes a fatal misjudgement before he finally unravels this complex and frustrating case.