At home, I was elated to be able to steal full days with my two children, both of whom had been born during my time working at the White House. Rían was nine months old, and Declan was 3. Like so many working parents, I was all too aware that I would never get to redo the parts of their early months and years that whirred by during 14-hour days on the job. I told myself that I was “binging” in my work life, and that the day would come when I would binge with my family, creating a permanent home for the four of us. Still, every couple of months I had tried to step back to assess whether I was getting enough done in my job to justify all the time away. Even during productive periods, I never felt great about my choices.

In this short spell before I descended again into full-time national-security work, I relished the time with Rían, who was nearly walking, and Declan, whom I taught to swim and brought to his first Washington Nationals baseball games. Then, in late May 2013, the main White House lawyer reviewing my files called to inform me that I had cleared the vetting process. My nomination would be announced imminently.

Samantha Power: Bystanders to genocide

In a remarkable coincidence of timing, Cass and I had been invited to dine with the president, Michelle Obama, and a few of their friends at the White House residence that very night. In anticipation, I had recruited my stepfather, Edmund Bourke, to make the drive down from New York to babysit. Eddie, as he was known, had become my stepfather when my mother moved my 5-year-old brother and 9-year-old me to Pittsburgh from Dublin, Ireland, in 1979.

A few minutes late, we were escorted up to the Obamas’ home and out onto their balcony overlooking the National Mall. Obama was already holding forth, and as we entered, Cass accidentally knocked over a glass. Obama laughed, recalling Cass’s notorious messiness when they were colleagues at the University of Chicago Law School.

“Leave it to Cass,” the president said, “to break the White House.”

After half an hour of small talk on the outdoor portico, we were called to dinner. Just as I walked back into the residence, my phone rang. I had given Eddie explicit instructions for feeding Rían, who was a fussy eater. He was now calling me in a state of panic, unable to find Rían’s pumped milk. Instead, he had settled on something white that didn’t smell like milk and wasn’t flowing through the small hole in Rían’s bottle, causing her to complain loudly.

Realizing that he had mistakenly attempted to feed her rice water, I ducked down the hallway to try to calm my frazzled babysitter while the president treated the other guests to a quick stop in Abraham Lincoln’s bedroom, showing them the only copy of the Gettysburg Address personally signed by the 16th president.

Explaining the logistics of baby care to Eddie by phone was like trying to explain the complexities of a new tech gadget: What seemed straightforward to me just wasn’t obvious to a man in his 70s. He became frustrated, I then grew exasperated, and both of us ended up practically shouting. This had happened many times before, but never in such close proximity to Lincoln’s bedroom. As our conversation escalated in its inevitable way, I suddenly heard a voice behind me.