Language/French/Grammar/Agreement-with-a-preceding-direct-object-in-a-relative-clause-when-the-participle-is-followed-by-an-infinitive
As in the case of preceding direct object pronouns, when a verb is preceded by a direct object which is the head of a relative clause and followed by an infinitive, the participle only agrees when that head is the implied direct object of the verb containing the participle and the subject of the infinitive. This means that there will be agreement in cases like the following:
- Nathalie a vu une énorme roche écraser sa maison
Nathalie saw a huge rock crush her house
- Voilà l'énorme roche que Nathalie a vue écraser sa maison
There's the huge rock which Nathalie saw crush her house
- On a entendu les voix résonner dans la caverne
We heard the voices echoing in the cave
- Ce sont les voix qu' on a entendues résonner dans la caverne
Those are the voices we heard echoing in the cave
But no agreement in cases like the following:
- Nathalie a vu écraser sa maison par une énorme roche
Nathalie saw her house crushed by a huge rock
- C'est sa maison que Nathalie a vu écraser par une énorme roche
It's her house that Nathalie saw crushed by a huge rock
- Hubert-Jean a regardé détruire la forêt par des bulldozers
Hubert-jean watched the forest being destroyed by bulldozers
- Voilà la forêt que Hubert-Jean a regardé détruire par des bulldozers
There's the forest that Hubert-Jean watched being destroyed by bulldozers
As in the case of preceding direct object pronouns, the types of verb which give rise to these contexts are perception verbs, movement verbs and laisser (but not faire).