Mateo finds a strange black rock while walking in the hills. A physicist discovers after extensive study that it interacts with its environment, displaying awareness and self-determination. It is so completely different than any other biological form and operates on completely different rules. Yet it interacts with its environment and displays will and self-determination. Is it alive?

While walking with his father in the hills, Mateo, an eight-year-old boy, finds an odd-looking black rock. He takes it home and begins to develop a relationship with it that no one else understands. He names it El Caja (the box) and it becomes his pet rock.

One day, the rock gives an electrical shock to his cousin while they are playing with it. This pushes his father Leon to take it to a physicist and electrical engineer to study it. The physicist discovers many odd things about the rock such as its ability to generate varied electrical currents and magnetic fields.

He later discovers the rock displays an awareness of, is able to interact with it, and change it. The rock is not made of anything resembling biological matter and operates on a whole different set of physical laws.

After more study and the help of a cryptologist, he is able to develop a way of communicating with the entity. Even with having these tools, communication is challenging. The entity's perception the species doesn’t have much of a common perspective. Shape and form make little sense to it because its perception is based on electromagnetic fields. In short, it perceives the world the way atomic physics defines it.

For some unknown reason, El Caja can communicate with Mateo through some type of telepathy riding on magnetic fields. With this added element they are able to discover from the entity that it comes from the earth, is one of its kind, and has been there since the dawn of time.