Movie
The Metropolitan Opera: Così Fan Tutte
Narrative tropes
You Can't Trust Anyone
mediumThe entire plot turns on a conspiracy of trusted figures working against the women: their fiancés (Ferrando and Guglielmo) orchestrate the deception from within, the household's own maid Despina is recruited and disguises herself as a doctor and notary to advance the scheme, and the mastermind Alfonso operates as a trusted philosophical companion. All three core requirements are met: (1) major betrayal by trusted characters — the fiancés are the very 'Albanian strangers' seducing them; (2) a hidden conspiracy within an ostensibly safe circle — Alfonso, Despina, and both officers all conspire together; (3) the protagonists discover at the final reveal that they were manipulated throughout. Signals confirmed: 'a major ally is revealed as a traitor' (both fiancés unmasked), 'the household/institution the protagonist trusts is secretly compromised' (Despina recruited into the deception), and 'the true enemy was hiding in plain sight among allies' (the Albanian strangers were the fiancés all along).
About this trope: Trusted allies, institutions, or authority figures are secretly working against the protagonist. Paranoia is justified because betrayal is real and pervasive.
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Full plot (spoilers)
Così fan tutte ("All Women Do Thus") is Mozart's 1790 comic opera in two acts, presented here in a 2014 Metropolitan Opera HD Live broadcast conducted by Music Director James Levine. The story is set in Naples and centers on a cynical philosophical wager. Don Alfonso, a worldly-wise philosopher, bets two young army officers — Ferrando (engaged to Dorabella) and Guglielmo (engaged to Fiordiligi) — that their fiancées cannot remain faithful if put to the test. The officers confidently accept the bet. Following a staged farewell as they pretend to leave for war, the two men return almost immediately in disguise as Albanian strangers, each attempting to seduce the other's beloved. Despina, the sisters' scheming maid, is recruited by Alfonso to aid the deception, at one point disguising herself as a doctor and later as a notary. In Act 1, Fiordiligi resolutely rebuffs the advances of the disguised Ferrando, while Dorabella shows signs of wavering. In Act 2, Dorabella quickly gives in to the disguised Guglielmo, surrendering the locket bearing Ferrando's portrait. Fiordiligi puts up a longer moral struggle but ultimately capitulates to Ferrando's persistent romantic entreaties. When the "soldiers" appear to return from war, the disguises are stripped away and the true identities of the suitors are revealed. Alfonso calmly announces "Così fan tutte" — thus do all women — vindicating his cynical bet. The opera closes ambiguously: the couples are reunited, but the experience of betrayal and disguise leaves the nature of their resumed engagements deliberately unresolved. The 2014 Met production stars Susanna Phillips as Fiordiligi, Isabel Leonard as Dorabella, Matthew Polenzani as Ferrando, Rodion Pogossov as Guglielmo, Danielle de Niese as Despina, and Maurizio Muraro as Don Alfonso.
Sources: Wikipedia, Fandango, TMDb overview