The armoured silhouette was Ankylosaurus.

I expected a lock. Something hidden in the tail club, perhaps. Another convenient shape to turn into a clue.

The notebook gave me a scene instead.

The animal stood across the doorway. Its head faced into the dark. Its tail pointed towards me.

It wasn't keeping something out.

In the drawing, it was keeping something in.

I sat with that for a while. The skeleton hadn't changed. My first interpretation had. Armour could make me think of a protector. The same armour, facing the other way, made me wonder what needed containing.

I drew the scene as a guardian at a gate. Then as an animal blocking a narrow path. Then as nothing more than a model beside a notebook.

Three pictures. Three different problems.

On the last picture, I drew the margin marks together. Split shadow. Three points. Hollow curve. Fan. Wing edge. Waterline. Threshold. Bar.

The bar closed the shape.

It was complete, but I still couldn't read it.

I started connecting the marks as if they were parts of one creature. Teeth. Wings. Horns. Armour.

A dragon, inevitably.

The notebook's reply was immediate.

That is the easy answer.

Under it was a question I wished I had asked first.

If this is a creature, why does it have a door?