From Le mystère de la chambre jaune (Gaston Leroux):
[U]ne terrible aventure que Joseph Rouletabille eût voulu savoir, me disait-il, oubliée pour toujours.
My first instinct was to translate eût voulu savoir [...] oubliée as "would have liked to forget" but then I realized oubliée is a past participle rather than infinitive.
My question is, is this a valid construction? And if so, I'm guessing the correct translation is "would have liked forgotten," but I don't really see how you can get that meaning from savoir.