Clark Sr. disrupted his son's career when he showed up drunk at the 15th Precinct, having been forced into retirement then turned into an IAB informant as a result of his involvement with the prostitute.
Clark Jr. had been dating Rita Ortiz, but the relationship ended when he pushed her away while grieving his father's death.
Clark Jr.'s bipolar ex-girlfriend, Dr. Jennifer Devlin (Chandra West), later died of a prescription drug overdose.
As a result of the tragedies, Clark Jr. experienced a brief, ugly period where he was often drunk and had a number of indiscriminate sexual encounters, causing at least one of the squad's cases to be ruined in court.
With Sipowicz's help, Clark Jr. righted himself, and soon began dating Assistant District Attorney Laurie Munson.