Why does Father Thomas lie about Francois' letter?

What causes Father Thomas to lie to Marie-Loup about Francois' letter? Is it because he so dearly loves Marie-Loup that he couldn't stand the thought of her leaving Quebec to go off with Francois to Europe or wherever? Is it due to his concern for her well-being, i.e. protecting her (and her daughter) from the possible dangers of such a move in a climate of political upheaval?

My gut feeling is that he dearly loved Marie-Loup and couldn't stand the thought of living without her nearby and under his shepherding care. In other words, he knew that if he told her the truth Marie would go off with Francois and it would end his relationship with Marie forever, limited as it was.