[s6e11] Back In The Day -

: Played by guest star Treat Williams , who becomes a recurring character throughout the series.

In this episode, Frank Reagan's leadership is tested when his former partner, Lenny Ross, decides to publish a tell-all book about their early years on the force. The book threatens to expose potentially damaging details about Frank's past, leading to a conflict between Frank's loyalty to an old friend and the need to protect the NYPD's reputation. [S6E11] Back in the Day

: Frank must navigate the fallout of the book while Garrett Moore warns him of the political repercussions. : Played by guest star Treat Williams ,