Though technically the finale (spanning episodes 21 and 22), the season 4 conclusion involves a massive secret being revealed.
: "Asylum" (Part 1 of the S4 finale). You can find technical and plot discussions on Wikipedia . [S4E21] The Last Word
Season 4, Episode 21 is It features a major resignation and a high-stakes investigation. Though technically the finale (spanning episodes 21 and
: "The Double Death of the Dearly Departed." Discussion regarding character motivations for this episode can be found on Reddit . The Blacklist finale recap: 'Mr. Kaplan: Conclusion' [S4E21] The Last Word