Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Doctor’s Obsession vs. Barbara’s Fear
S1E5
·
The Dead Planet
To
TARDIS breakdown forces city expedition
S1E5
·
The Dead Planet
Why These Connect
The narrative assertion
"The travelers' desire to explore the city leads directly to the TARDIS malfunction, as the need for mercury forces them to venture into the very city Barbara wanted to avoid. The Doctor's initial desire to explore the city directly creates the situation where the companions now need to go to the city."
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.