On a warm spring afternoon 22 years ago, my dad and I sat chatting on the lawn outside a clinic where my mother, who suffered from early onset Alzheimer’s Disease, was having an MRI. My dad had been her caregiver for nearly 10 years. During a lull in our conversation, he took his worn leather wallet from his pocket and, from between two old photographs, he pulled out a lock of hair. “I think it’s time I told you about Helen…” he began.