Danny Messer has developed a deep trust in him. In Season 2 the team began investigating an old murder case after remains dating over a decade ago were found in a football field and tied to a street gang Danny and his older brother Louie once ran with when Danny was a youngster. Danny denies having any connection with the remains and Mac displays his trust in him by telling him "I believe you". Louie is later beaten up as retribution and Mac is the first person Danny confides in. Danny, however, is the last to find out about the romance between Mac and Peyton (episode 3.16, "Heart of Glass"). Mac was a witness at Danny's marriage ceremony to Lindsay Monroe and the godfather of their daughter Lucy.