Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Vicki Volunteers as Hostage
S3E1
·
Four Hundred Dawns
To
Chumblies test TARDIS defenses
S3E1
·
Four Hundred Dawns
Why These Connect
The narrative assertion
"Vicki volunteers as hostage, so the Doctor and Steven return to the TARDIS and find Chumblies attempting to break in."
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.