Indirect objects that answer the question "by whom"
Here is a sentence from Chapter Seventeen of Huckleberry Finn. The sentence appears in a grammar worksheet:
When I got to the three log doorsteps I heard them unlocking and unbarring and unbolting.
My English teacher stated that "them" was an indirect object, and unlocking and unbolting was a direct object, as that is what was being directly heard. She states that indirect objects can answer the questions "by whom", referring to the direct object. (The doing could be done by the indirect object.) This doesn't really make sense to me. My first impression was that them was the direct object and the participles unlocking and unbolting were modifying them. So, can an indirect object in a sense do the action of a gerund direct object? Any help is welcome!
Solution 1:
Your English teacher should cut wood but not teach English.
There are two special verb constructions with accusative (= direct object in English) + a verb form. (Actually there are more but I don't want to write a grammar here.)
1 - I saw the bridge explode. (noun + bare infinitive, emphasis on fact).
2 - I saw the bridge exploding (noun + present participle / gerund, it can be either form). In a film this would correspond to a close-up, evoking the scene of the exploding bridge. You can derive such a construction, eg by saying:I saw the bridge at the moment of exploding - or: I saw the bridge, it was exploding.
The verb construction verb + noun + bare infinitive is 2000 years old. It was one of the favourite constructions of Roman authors. And an English teacher should know this construction and not tell fairy tales.
Solution 2:
When I got to the three log doorsteps I heard them unlocking and unbarring and unbolting.
Your English teacher is wrong, I’m afraid.
There is no indirect object in your example. "Them" is the direct object of "heard". The participial clause "unlocking and unbarring and unbolting" is not the direct object, not an object at all, though it is a complement of "heard". Such clauses are often called 'catenative', from the Latin word ‘catēna’ meaning chain.