Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
TARDIS locked by Arbitan’s blackmail
S1E21
·
The Sea of Death
To
Arbitan traps crew with force field ultimatum
S1E21
·
The Sea of Death
Why These Connect
The narrative assertion
"The Doctor discovers an invisible barrier preventing access to the TARDIS, then Arbitan's disembodied voice reveals he erected the force field and is blackmailing them."
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.