Who are You?

Mateo was in Gretta's room, he was there because Gretta had called to meet him there. Mateo was confused as to why Gretta was looking for him and asked to speak to him one-on-one. 

Gretta, who was sitting enjoying her glass of hot tea, invited Mateo to join her in the chair across from Gretta. She warned that what she was about to say would take some time, so Mateo should sit there and listen. 

It was during that meeting that Mateo first heard about the plan for him to most likely be sent as Orlin's spy to find out Rhys' whereabouts. 

There was no specific talk between Leon or Shan with Gretta about Mateo, but Gretta could already guess what steps Leon had thought of and what support Shan would give. Therefore, she called Mateo to warn him. 

"If that really happens, then accept the offer Leon made. Be a spy for Orlin according to his orders."