Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Book unleashes forbidden energy
S17E21
·
Shada Part 1
To
Dangerous book revealed in Chronotis study
S17E21
·
Shada Part 1
Why These Connect
The narrative assertion
"Parsons' attempt to scan the book with an x-ray scanner causes it to explode and glow, which forces Chronotis to reveal the book's true nature and origin ('The Worshipful And Ancient Law Of Gallifrey') to the Doctor and Romana, driving the subsequent plot."
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.