Vera Claythorne definitely has some unusual events behind her: she feels lucky to have the "third-class" job she does, since she knows "people don't like a Coroner's Inquest—even if the Coroner did acquit me of all blame!" Even if she isn't to blame for a death, she is still very carefully not thinking about "Hugo," who seems to have been part of the business though we're not sure how.
Philip Lombard has "an arrogant almost cruel mouth," and, according to Vera, looks as though he's "seen some interesting things." We know he was "literally down to his last square meal," though we don't know how he ended up in such a "tight place." We also know that while he may not want to do anything illegal now, he certainly has in the past: "In Lombard's past actions legality had not always been a sine qua non... But he'd always got away with it!"
The stern Miss Emily Brent mysteriously references "last year's summer holiday," and vows that this one will be different.
General Macarthur finds that people are avoiding him because of "that damned rumor!" Somebody has talked, and the events of thirty years ago have leaked out...though we don't know what those might be.
Dr. Armstrong is doing well now, but thinks it's lucky he "managed to pull himself together in time after that business ten—no, fifteen years ago."
Mr. Blore knows who everyone is and is constructing a fictitious personality for himself—very suspicious.