When Richie and Mac are talking about Kristin's death, Methos walked in without either sensing his presence.
When Duncan asks Methos if he should call him Adam, Methos replies "Only you and Joe" know I'm am Methos. To the rest of the world I am Adam Pierson.
In a previous episode, Duncan had already addressed him as Methos with Amanda present.
When Mac is talking to Richie after Kristin is killed, Mac says he was 75 when he first met her. Being born in 1592 and meeting Kristin in 1659 means he was in fact "only" 67 years old.