Answer the following questions briefly:

At what point does it become clear that the nobleman's hospitality was a trap?

When the nobleman Marquis de Thevenin revealed that Victor Lesuer, the man whom the executioner disguised Robichon killed, was none other than his own son, Robichon realised that he had been trapped. The nobleman also told Robichon that his drink had been poisoned to which he became paralyzed with terror.