If you are talking about the actual scheme or plot inside the episode's narrative:
If you are listing episodes, you generally do need an article. Example: "Next on the watchlist: [S7E10] Master Plan." [S7E10] Master Plan
Depending on how you are using the title in a sentence, the "proper article" changes based on standard English grammar: 1. Using it as a Title If you are talking about the actual scheme
The episode title refers to the tenth episode of the seventh season of The Clone Wars . [S7E10] Master Plan
" The '[S7E10] Master Plan' episode is a fan favorite." 2. Referring to the "Plan" within the story
Use this if you are introducing the concept for the first time. ("Darth Sidious set a master plan into motion.") 3. In a List or Citation