On July 27, 2008, I took my daughter Anna to her best friend Hazel’s birthday party in Palo Alto. I think they were both 6 years old. The party was at Rinconada Pool, a local public pool that you could reserve for private parties on weekend mornings.

It was still cold when we got there, before 10am I think, and they hadn’t opened the pool yet. Anna went off with her friends, and Hazel’s parents and various other adults were busy setting up plates…