Narrative Connection
How these two moments in the story relate
Why These Connect
The narrative assertion
"Chen's overconfidence in delivering the taranium core (Episode 20) emboldens him to believe his alliance with the Daleks is unassailable, leading him to deliver Steven and Sara as prisoners in Episode 21 expecting praise."
inferred by llm_cross_episode_arc
Why This Matters Across Episodes
The longer arc this connection carries
This is the primary causal link in Chen's arc. His early boasts about his indispensability ('I hope that the Daleks will not suffer any more setbacks which could upset the plans for our conquest of the universe') directly lead to his downfall in Episode 21 where he delivers prisoners to the Daleks, believing they will reward him.
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.