The sun bathed the backyard in a soft warmth, casting a golden hue over the vibrant garden roses and swaying trees. Thirty minutes after meeting five-year-old Chris, who kept looking at me as if I’d broken a favorite toy of his, I suggested we go out to the backyard to get some sun and fresh air.

Silvia hadn’t been kidding when she said he had a difficult temperament. From the moment she introduced me to him as his nanny, he’d started throwing tantrums and refused to listen to ...