Relative pronoun

If the third people are the subject of the action the relative pronoun 'whom' is used:

The girl with whom I spoke was from Argentina – La muchacha con quien hablé era de Argentina

The man to whom I gave the key was the owner – El hombre a quien le di la llave era el dueño

The writer from whom I received this script is well known – El escritor de quien recibí este guión es bien conocido.