Tom Cavanagh Is Set to Reprise His Guest Role in 'Blue Bloods' — Details on His Return

For a long-running police procedural drama like Blue Bloods, guest actors tend to make the rounds. The series follows the Reagan family, mostly composed of members of law enforcement. There's assistant district attorney Erin (Bridget Moynahan), police officer Jamie (Will Estes), Commissioners Henry (Len Cariou) and Frank (Tom Sellick), and Detective Danny (Donnie Wahlberg), each of whom operate in different positions of the U.S. legal system.

With over 13 seasons and counting, the lore of Blue Bloods has expanded greatly as it explores different aspects of each Reagan's work and personal life. To that end, many guest stars portray different characters with unique relations to the Reagans.

In tonight's new episode, Tom Cavanagh (The Flash) makes a return to the series after 10 years, reprising his role from all the way back in Season 4. Read on for the details of his return.

Tom Cavanagh first appeared in Blue Bloods in Season 4, Episode 11, "Ties That Bind." He portrayed Michael "Mickey" Patrick, a childhood friend of Danny's who returns to the New York area to visit. As children, Mickey often got Danny into trouble, prompting Frank and Henry to put some distance between them.

With his return, Mickey proved that old habits die hard after Danny learned about his connections to a Florida-based crime family. Though Danny is able to help him out of his situation, their relationship becomes strained.

That's the last we heard of him for more than 10 years. When last Mickey and Danny spoke, Danny urged him to go on the straight-and-narrow in order to keep himself safe.

In Season 13, we'll get to see exactly how that played out over the past decade. CBS recently confirmed that in tonight's episode, "The Big Leagues," Mickey approaches Danny once more as he attempts to search for his missing fiancé.

Meanwhile, Erin goes on one more stakeout before running for DA, Jamie catches a former officer committing a crime for just causes, and Frank deals with a salacious murder confession.

Past traumas and future career moves are at the forefront for the Reagans moving forward. New episodes of Blue Bloods premiere Fridays at 10 p.m. EST on CBS.