I hear the sound before my eyes discover its source. It is the low hum of a child, steady and unwavering. It is not troubled or pained, just persistent.

I recognize it immediately, because I know it intimately. It was the soundtrack of Ryan’s youth.

I search the airport gate for its source. Despite the lack of sleep and focus (would it kill the Bruins and Blackhawks to end a game in regulation on a travel day? I mean, really!) I discover him immediately. Once my eyes lock in on the child, I am not surprised at what I see.

I have seen it before.

Many, many times.

I know. Instantly. Does his mother?

The child is a boy of perhaps two or three. He is lying on his side on the floor of the gate, playing with a toy car.

Just as I knew he would be.

He slowly pushes the car back and forth, humming the pretend sound of an engine.

Steady. Persistent. Unwavering.

His eyes do not divert from the car. He is lying so he can watch it even closer, eyes locked in on its back-and-forth motion.

There’s another thing. He is playing next to his stroller. He rolls his car back and forth in front of the stroller’s wheel, which is right in front of his eyes.

Ryan probably spent composite years in that same pose, engaged in that same activity, making that same sound. Eyes locked on the wheels. Pushing the cars back and forth.

Back and forth.

Back.

And.

Forth.

And that sound, the low hum of the car’s pretend engine. How many hours did I listed to that sound? It is imprinted upon my brain.

I look over again. The child is not distressed, not pained. Aside from the noise, not bothering anyone. A few of the other passengers look up, but the woman I assume is his mother, sitting just on the other side of his stroller, does not.

Suddenly, my brain is racing. Has she had a developmental evaluation? Seen an early intervention specialist? Does she have a diagnosis?

I know.

Does she?