The hospital pharmacist slid three bottles of pills across the counter, gave my wife a form to sign, and reminded her that this was not the corner drugstore. The pharmacy knew how many pills had been dispensed, he said; it would know how many had been consumed; and it would expect her to return the unused pills before she left the country. The pharmacist made it clear that he was not only in touch with our doctor but with the company supplying the medication. They would know if she broke the rules.

Evelyn said she understood and slipped the brown glass bottles into her purse. She and our 11-year-old son, Sam, were jet-lagged. They'd flown from San Francisco to London the previous day, December 19, 2012. Now, 30 hours later, it was just after 7 pm. They'd been at the Great Ormond Street Hospital for Children since midmorning. Sam had been through a brain-wave scan, a blood test, and a doctor examination. Some gel left in his hair from the brain scan was making him grumpy.