Causal
strong strength
Narrative Connection
How these two moments in the story relate
From
Tegan seizes ambulance to save the Doctor
S19E1
·
Castrovalva Part 1
To
Nyssa and Tegan uncover the Master's trap
S19E1
·
Castrovalva Part 1
Why These Connect
The narrative assertion
"Tegan's ambulance commandeering leads directly to her and Nyssa's later realization that the TARDIS is on a pre-programmed course ('Event One'). The urgency and resourcefulness she demonstrates in escaping security forces at the Pharos Project make her subsequent navigation of the TARDIS central to the plot's survival."
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.