In your sentence the noun that the adjective afraid modifies is king which (the noun) is omitted here.

Your sentence can be read this way:

The king afraid that the dream should prove true…

So it is not the dream that is afraid.

Note that there is an implied "that" in the original sentence.

In your sentence the noun that the adjective afraid modifies is king which (the noun) is omitted here.

Your sentence can be read this way:

The king, afraid that the dream should prove true…

So it is not the dream that is afraid.

Note that there is an implied "that" in the original sentence.

In your sentence the noun that the adjective afraid modifies is king which (the noun) is omitted here.

Your sentence can be read this way:

The king afraid that the dream should prove true…

So it is not the dream that is afraid (modified).

In your sentence the noun that the adjective afraid modifies is king which (the noun) is omitted here.

Your sentence can be read this way:

The king afraid that the dream should prove true…

So it is not the dream that is afraid.

Note that there is an implied "that" in the original sentence.