疑わしいことが一つ残っている。

doubtful; questionable; uncertain; disputable; suspicious

thing; matter; incident; occurrence; event; something serious; trouble; crisis; circumstances; situation; state of affairs; work; business; affair; after an inflectable word, creates a noun phrase indicating something the speaker does not feel close to; nominalizing suffix; pretending to ...; playing make-believe ...; alias; aka; nickname; alternative name; also known as

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

one; for one thing; only; (not) even; just (e.g. "just try it")

to remain; to be left