Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Frogman corpse reveals deadly island secrets
S1E21
·
The Sea of Death
To
Acid sea revealed and frogman discovery
S1E21
·
The Sea of Death
Why These Connect
The narrative assertion
"After discovering the acid sea, Susan goes to the TARDIS; returning, she then finds a frogman's footprint, which leads her to the pyramid."
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.