Wagner’s Flying Dutchman, in which Yevgeny Nikitin was going to sing the title role before news came out that he once had a swastika inked into his chest, “is about a man with a secret, a youthful mistake that he spends a long, long time paying for. … But while the details [of Nikitin’s story] keep altering, their implications are profound for a festival that cannot and should not stop thinking about its past.”