Many verbs can be followed by two objects – an indirect object and a direct object. The indirect object usually refers to a person and the direct object usually refers to a thing.

Two structures are possible.

Subject + verb + indirect object + direct object

He showed me a letter.

She gave her sister a car.

The indirect object can go after the direct object. In this case, we use the preposition to or for.

Subject + verb + direct object + preposition + indirect object

He showed a letter to me.

She gave a car to her sister.

Both of these structures can be made passive.

I was shown a letter (by him). (Here the indirect object becomes the subject of the passive clause.)

Her sister was given a car (by her). (The indirect object becomes the subject of the passive clause.)

A letter was shown to me (by him). (Here the direct object becomes the subject of the passive clause.)

A car was given to her sister (by her). (Here again the direct object becomes the subject of the passive clause.)

Of these two structures, the one in which the indirect object becomes the subject of the passive clause is probably the more common.