Causal strong strength

Narrative Connection

How these two moments in the story relate

Why These Connect

The narrative assertion

"The Doctor discovering that he is not alone behind the mirror allows Romana to eventually escape into that same realm, leading directly to the climax where Romana appears to save him from the knife-wielding Tharil."

About Causal Connections

A directly causes B. The first event sets forces in motion that produce the second. These are the load-bearing connections of plot--remove one and the story structure collapses.