It is a curious thing, the death of a loved one. We all know that our time in this world is limited, and that eventually all of us will end up underneath some sheet, never to wake up. And yet it is always a surprise when it happens to someone we know. It is like walking up the stairs to your bedroom in the dark, and thinking there is one more stair than there is. Your foot falls down, through the air, and there is a sickly moment of dark surprise as you try and readjust the way you thought of things. Lemony Snicket

For months after my son Jimmy died, I kept expecting him to return. To walk down the stairs. To emerge from the back patio. To come trailing down the hallway, following his dad after an outing. Even though I knew he was forever gone, my brain couldn’t seem to wrap itself around that simple fact.

During those grief-stricken days, his absence made no sense to me. I had been with Jimmy practically every moment for months, leaving his side only to use the bathroom, take a shower or grab something to eat. I had watched his physical decline in real time as the cancer occupied more and more real estate in his brain and spine. Seen him lose his ability to walk and eat more than a few bites. I had lain curled at his side as he sunk into a coma, born witness to his spirit leaving his body, walked him all the way home. i had met the undertakers at the door after standing beside his cold body, willing my brain to understand Jimmy was no longer here. And still the feeling of his presence persisted.

I started to wonder if I was just in denial or actually losing my grip on reality and which one was worse. Part of me didn’t care. There were so many days when it felt as if my very survival hinged on Jimmy not be fully gone, so I’d lean into the feeling. Burrow into the idea that he was just upstairs taking a nap or away at school.

It was only a decade later when I read Mary-Frances O’Connor’s The Grieving Brain that I came to understand what was happening and how completely normal it is.

O’Connor begins her book with a metaphor that has a simple premise – someone has stolen your dining room table. You awake in the middle of the night and wander down the hall in search of a glass of water from the kitchen. You move a bit to the right, expecting your hip to bump the corner of the table. Instead, you feel nothing but air. And you know immediately something is wrong. How can you feel what isn’t there?

O’Connor explains that we walk in two world simultaneously – the physical world and a virtual one. In our heads, we create a map for that virtual world which allows us to navigate our house and other familiar places in the dark. We know where the furniture is, the doors and walls and can move around in the darkness without walking into them.

We also place people on our virtual map. The family members or friends we live with and expect to find when we come home from work or eating breakfast the next morning. One or both parents in a childhood home or assisted living. Siblings and children in dorms or apartments in other states. Even when we can’t see our loved ones, we expect them to be in a certain location, a specific place on our virtual map.

This is what has us surprised when one of our kids comes home from college unexpectedly or returns early from a party. It’s why we get disconcerted if a close friend or family member has ventured far from home without telling us. We don’t expect them to be somewhere else on our virtual map, just as we don’t expect the dining room table to be missing.

Now imagine how flummoxed our brains are when one of our loved ones dies. An unexpected loss can feel impossible to comprehend, but even a witnessed death like Jimmy’s can create confusion and disorientation. It still makes no sense to me that my then 21-year-old son is dead. He should be here, even if he’s living somewhere out of my sight.

There were moments after Jimmy’s death when it felt as though the molecules in the space he should have been occupying would coalesce into the shape of his body. His energy felt present and tangible.

But as time marched on and Jimmy didn’t reappear, my brain reset, taking note of the fact that he hadn’t come downstairs for dinner for weeks or months, hadn’t texted or called to tell me about what he had learned that day in one of his religious studies classes, hadn’t called down from his room to say goodnight or tell me that he loved me. In the face of this data, my brain redrew its virtual map and removed Jimmy from it.

For a long time, all I felt was Jimmy’s absence until another part of my brain called him forth. I’d hear a song he loved, visit a place he’d been, see a look on Molly’s face or hear his voice in my head reminding me to be kind. Sweet reminders that he is still here, if only I am willing to keep looking for him.