There's a roomful of painters laying down crisp white paint on the walls of a vacant apartment -- when a splash of red shows up on one of the rollers. Something's seeping through from the next floor up...where a bullet-riddled body is lying sprawled across the carpet.

The body is that of Patrick Coonan, a known member of an Irish crime family based in Hell's Kitchen. Castle and Beckett drop by the auld working-class pub owned by the family's head, Finn Rourke, where Finn gives them no welcome at all and rails about the rival West Indian gang running drugs in his territory, a trade he says he abhors. The dead man, it seems, had been looking into that drug trade, and was about to hand his findings to the FBI when the killer caught up with him -- a fact that doesn't sit well with either Finn Rourke or the victim's brother, Dick.

The key to the drug-trafficking scheme proves to be Johnny Vong, the Vietnamese Don Ho of the get-rich-quick infomercial circuit, who's not quite the man his DVDs describe. But the key to the murder may be Beckett herself -- because hard forensic evidence says Patrick was killed by the same cold-blooded professional who murdered Kate's mother ten years earlier. And when a deadly showdown explodes in the precinct's own offices, saving Castle's life may just cost Beckett the answers to the mystery of her mother's death.

The commentary track:

Rarely has so much anticipation been rewarded with so little payoff.

The teasers for "Sucker Punch" emphasized taut, life-changing drama centered squarely on Beckett and the resolution of her mother's murder. But in the episode as aired, the matter doesn't even come up till halfway into the hour, and the script manipulates nearly every aspect of the murder investigation in ways that undermine dramatic tension rather than heightening it.

In both last season's "A Death in the Family" and the present episode, consulting pathologist Dr. Clark Murray (Robert Picardo) profiles the murderer of Johanna Beckett and Patrick Coonan as a professional contract killer -- an expert one, who's been practicing his craft for more than a decade, and has left investigators few clues to his existence or identity. This suggests an individual who, though dangerously violent, doesn't take foolish risks or draw undue attention to himself.

SPOILER WARNING: The following discussion reveals the murderer.

Yet in "Sucker Punch", Dick Coonan makes every mistake in the book.

A smart assassin keeps his work and his personal life separate; Dick murders his own brother using his standard M.O. A wise professional distances himself from his current and former victims; Dick goes out of his way to stalk and taunt Beckett. And a shrewd hit man cuts and runs when necessary; instead, Dick attempts to choreograph a $100,000 con job that goes predictably and disastrously wrong. The Dick Coonan we see in "Sucker Punch" is arrogantly and fundamentally stupid -- a characterization totally inconsistent with that of the skilled, patient contract killer who's supposed to have murdered Johanna Beckett.

Worse, the script prevents Beckett from overcoming her personal demons by using her superior investigative skills. Captain Montgomery says she's the best detective he's ever trained -- but in this episode she's scarcely allowed to detect. She doesn't catch the killer by following the forensics, tracing his tools, unraveling the web of contacts his prior clients must necessarily have shared. Instead, he literally comes to her, practically begging to be caught. Nor does it help that the key deduction, involving Dick's use of the phrase "her killer", is far less conclusive than the script suggests .Given Dick's connections, he could easily have known Beckett's history from other sources -- the hypothetical "Rathborne", his Irish contacts, or even old news reports.

Yet another difficulty is the lack of balance between the episode's three plotlines. The first few scenes begin what looks like a promising family drama involving Finn Rourke's Irish crime syndicate, but that thread fades out much too soon, regrettably taking James Cosmo's icy yet deeply nuanced Rourke with it. Then we're diverted into the drug-running scheme centered on "Johnny Vong", which becomes the hour's dominant (and best-constructed) mystery plot, featuring an energetic, lively performance by Eddie Shin. Jay R. Ferguson's Dick Coonan is better as Shin's foil in the drug plot than when he's belatedly revealed as the killer; part of the problem is that he's just too bulky, moving more like a football player than a ninja.

As disastrous as the script is, the episode as a whole is surprisingly watchable, due almost entirely to superior performances from stars Nathan Fillion, Stana Katic, and Ruben Santiago-Hudson as well as guest stars Shin and Cosmo; the latter's Finn Rourke is a character viewers should hope to see again. The Johnny Vong segments bring out the show's comic sensibilities to excellent effect, and once we get there, the resolution and aftermath of the climactic shootout are deftly staged. But as the story where Kate Beckett catches her mother's killer, "Sucker Punch" unequivocally fails on all counts.