So who was the black man
who died in the car with Tessa? What was the point of replacing Arnold with him? Maybe they wanted a chance to torture Arnold, but they could have simply killed them both at the same time and place. Also, we see a car tipped over to reflect the death. But if she was raped and otherwise tortured before being killed, why stage a car crash?
Also, they never really explained what they were doing at Lake Turkana. And unless it was a story made up to fuel the infidelity rumors, why did Tessa and Arnold spend the night together?