All the detectives scramble to solve the case, when the mother, in a family on vacation, is murdered during a holdup. The husband has a hard time dealing with the reality of him not doing anything during the situation and Felton's indifference. When the suspects are found Howard is convinced that the youth who confesses to the murder didn't do it.

Jake Rodzinski has trouble dealing with the verdict of the trial and takes justice into his own hands. Kellerman is back from a family wedding in Wisconsin picks up the case of the murder of Kenny Damon. Lewis is not allowed to know all the details of Kellerman's investigation, because of his past relationship with Rodzinski, their chief suspect. Bayliss is at odds with Pembleton over the disposition of a grilled cheese sandwich.

Lewis and Kellerman's investigation of a murder in a housing project puts them at odds with a civilian-patrol group, run by the Black Muslims. Munch is excited because Stan is scheduled to come back June 1st. Russert and Munch catch a case where both the victim and shooter are dead. She with Howard must decide whether to circumvent the so-called ""blue wall of silence"" among police officers when it is discovered that the officer on the scene didn't react in time. Barnfather stops Lewis and Kellerman's charging of a Muslim, until something is leaked to the newspapers. The ""big man"" is scheduled to come to the bar, but changes his mind, twice.

More drug-related homicides are occurring. Pembleton is still relegated to desk duty and now so is Kellerman. A federal grand jury investigation is being conducted that goes back to the time when Mike was in the arson unit. Frank is still not taking his medicine and getting ready for the range test. Brodie moves out of Munch's place and into Bayliss'. Lewis finds out that the witness to his drug homicide has been brought downtown. He goes after him and meets Stivers, a female detective in narcotics. Lewis's witness points toward Luther Mahoney as the initiator of the contract. They go to find the executor, who's been executed. Stivers pages Mahoney and he comes in for questioning, but they can't make a case that Danvers thinks will stick. Frank misses a passing grade on his test by four points.

A new Baltimore Sun reporter gets into the middle of Frank's investigation of the death of a county cop who was shot because of drugs. Gee likes her style. Mike's brothers, Drew and Greg, come to town, who want to take him and his boat to Miami to set up a charter service. Mike learns that they are on the run from a bookie that Drew owes $18,000. To pay that debt, they've stolen Babe Ruth's Baltimore uniform from another bookie with the intent of selling it. Lewis and Cox go in search of the Kellerman boys. They find them in jail where they spent the night after trying to return the uniform.

Mike and Julianna wake up the morning after a night of drinking and passion. The investigation into Beau's death continues; Howard wants to be the primary while Frank tries to maintain control. Gee asks her to step aside and let him do the job with a more unbiased approach. The investigation creates some unlikely pairings: Pembleton with Gharty and Bayliss with Falsone and Munch on his own. Meanwhile, Howard and Russert make arrangements for Beau's funeral. Lewis and Kellerman's investigation into a homicide is stalled; when Kellerman's hangover laden police work is shoddy. When it appears as thought the investigation is going nowhere; Kay demands to be put on the case. Gee refuses. Because of his bad day and finding Julianna drinking with someone at the Waterfront Bar, Kellerman suggests that they should stop drinking. Frank tries to call Mary; eventually they connect and reconcile; with Frank saying that he is willing to give it all up. They find out who killed Beau, but when they go

While Pembleton is still interested in the housekeeper's ex-boyfriend, Ballard still thinks that the Wilson family needs to be looked at more closely. Also, a body is found at Camden Yards during a game between the Orioles and the A's. Falsone questions Stivers about the Mahoney shooting and that begins to make her nervous. Tensions mount because there appears to be a leak to the press within the unit about the Wilson case. Orioles' security wants the case quickly resolved. Munch and Kellerman have only 48,000 possible suspects. The victim is discovered to be a dead Yankees fan. Tim gets his old high school French teacher to help them check out the whereabouts of the housekeeper's ex-boyfriend. He is cleared because of his current incarceration in a Haitian prison, which leaves the Wilson men as more probable suspects. Are Gee and Pembleton protecting Felix Wilson because he is a prominent businessman in predominately black Baltimore, as outsider Ballard suggests? Munch and Kellerman g

The Wilsons go on television to offer a reward. The newspapers are making the Homicide unit look bad and Barnfather wants quick resolution to the case. The man (and his wife) who gave up Junior Bunk are murdered; Falsone and Lewis investigate. The only survivor, their young son, is brought in to find out what he remembers. His memories-- and a recorded phone message-- lead Stivers to believe a former member of the Narcotics unit is involved. The officer cops to a deal that implicates Georgia Rae Mahoney, though Giardella doesn't want to pursue that yet. Falsone's questioning of the Mahoney shooting leads Cox to doubt her actions at the time of the investigation. Incriminating evidence leads the detectives to Hal Wilson being their prime suspect. Frank goes to interview Felix and Hal Wilson; son and father confront some long-standing issues. Hal's confession is inadmissible in court, the Wilsons leave the Baltimore area, and the case remains officially open.

With the addition of the latest murder, the ""red ball"" investigation continues full force. The detectives and the returning Bayliss pose as priests in an attempt to flush out any leads. Munch's cover attracts two young thugs, but they prove to be nothing. Gee is called upstairs, where his performance doesn't sit well with Barnfather. Lewis turns up and seeks some help from Falsone. Pembleton receives a call that the two missing boys have been found. Pembleton and Stivers travel to collect them. Meanwhile, Gharty and Ballard find the pawnbroker who had accepted a stolen chalice. Cox and Bayliss prevent a drunken Kellerman from driving home. Ballard and Gharty use the pawn-receipt false address to track down the corner kid with whom they'd previously had a run-in. They bring him into the box and Gharty loses his cool. The kid is tough to crack, but Pembleton has an idea involving the morgue and a trip to the shore. While stumbling home, a drunken Kellerman decides he doesn't like the loo

A woman brings to the homicide unit her mystery-writer husband's videotaped declaration that his literary agent is responsible for his murder. Ballard and Gharty catch the case -- only there is no body or crime scene. Meanwhile, Munch and Bayliss investigate the death of an elderly woman that occurred during a break-in -- was it a homicide? Munch would rather leave for his weekend rendezvous with Billie Lou. Ballard and Gharty's investigation becomes a red-ball as they find evidence in the writer's office that a crime was committed. A break leads to the arrest of the literary agent and his accomplice, although Danvers can't guarantee a conviction. Falsone asks Ballard if she would like to go out Saturday night; just then the jury comes back. And a sharp-eyed juror insures that justice is done.

Danvers brings news of his appointment to the District Court bench as the investigation of a government official named Janine McBride continues in New York. Their prime suspect Chesley Purcell is dead and her shooter is in the hands of the Feds. The Baltimore detectives investigate the background of Chesley Purcell and it turns up the name of a man in prison who still appears to be running his organization.

This crossover starts on Law and Order S09E14 Sideshow (I).