Guest stars include Lily Tomlin, Jeffrey Donovan, Bruce Campbell, Jerry Orbach, Benjamin Bratt, Jill Hennessy, Chris Rock, Marcia Gay Harden and Jay Leno.
Pembleton and Bayliss investigate a body found at a burned-out warehouse and cross paths with arson detective Mike Kellerman, whose theories of the crime put him at odds with the pair.
Pembleton is thrown off balance by the change of scenery and the fact that he will soon become a father, while Howard (recently promoted to Sergeant) gets off to a bad start in her attempts to supervise the other detectives.
Munch's stab at a relationship with medical examiner Alyssa Dyer quickly goes sour, and when Pembleton finds that everyone in the office suddenly knows about Mary's pregnancy, he becomes enraged at Bayliss for telling the secret.
The fact that nearly every tenant has a criminal record, and the victim is missing both a boot and vintage motorcycle, leave the pair awash in potential suspects but short on evidence.
As detectives from Baltimore and New York connect a pair of poison gas attacks in the two cities five years apart, the prime suspect's wife is murdered to keep him from giving up any more information.
"[12][13] Guest star: J. K. Simmons as Alexander Rausch Lewis and Kellerman are sent to Pennsylvania to pick up Rose Halligan, a fugitive wanted in Baltimore for the murder of her husband.
As the evidence increasingly points to Jake's involvement in the shooting, Gee reflects on the changed culture of the police; in the old days, cop killers were shot on sight.
After the detectives learn the name of the man responsible for a long string of abductions and murders, they begin round-the-clock surveillance at his neighbors' house, waiting for him to come home so they can arrest him.
As everyone on the shift takes a turn, three topics keep coming up: the personal lives of the homeowners, Giardello's indecision about flying to California for his daughter's wedding, and rumors that Bayliss plans to leave the homicide unit or quit altogether.
A high-profile divorce lawyer is found dead in his own swimming pool, and a man claiming to be his son shows up in the homicide office with evidence to incriminate himself.
Meanwhile, Brodie tries to toughen himself up, Munch buys a VCR of highly questionable origin, and Kellerman tries to unmask the "Lunch Bandit" who has been stealing everyone's food from the office refrigerator.
Kellerman becomes the primary on a rash of drug-related killings that prove to be part of a turf war between two rival dealers, "Drak" Fortunato and Luther Mahoney.
Lewis and Kellerman investigate the death of a drug dealer in a housing project, but are hampered by the interference of a private security force run by Black Muslims.
A double shooting in another housing project leads Russert to file departmental charges against the patrolman who responded to the call, arguing that at least one of the victims might have survived if he had not waited to go in.
Pressures both on and off the job are mounting for the detectives, as Mary gives birth to the Pembletons' daughter Olivia and Lewis confesses to Kellerman that his marriage is already in trouble.
Returning for the fourth season of Homicide were Richard Belzer, Andre Braugher, Isabella Hofmann, Clark Johnson, Yaphet Kotto, Melissa Leo, and Kyle Secor.
The characters of Beau Felton (Baldwin) and Stan Bolander (Beatty) were written out by engaging in drunken, inappropriate behavior while attending a policeman/firefighters convention in New York City; as a result both were suspended for 22 weeks (the length of the season).
Law & Order stars Jerry Orbach, Benjamin Bratt, and Jill Hennessey played their characters Lennie Briscoe, Rey Curtis, and Claire Kincaid respectively in "For God and Country".