Just when it seemed as if everyone had forgotten about poor Walter Steele – seriously, Queen Consolidated loses two CEOs in five years, and the police barely notice? – he comes roaring back to center stage as Oliver, and Arrow, refocuses attention on the sinister plot that’s supposedly driving events. Love triangles, vendettas and parental issues are (mostly) pushed to the backburner, primarily because we’re just two episodes away from the season finale.

While the lurch back to Walter’s disappearance, signaled by a call from the only insurance company in the world antsy to declare a policy holder dead, is undeniably jarring after so many episodes in which his name has been barely mentioned (if at all), “The Undertaking” is easily the best installment of the series since February’s “Dead to Rights.”

That’s largely because after so many weeks of marching in place, the central plot finally lunges forward, resolving a handful of nagging questions – like “Where’s Walter?,” “What the hell is the Undertaking?,” “When will Ollie smarten up about his mother?” – and providing some payoff to viewers who have endured the surprisingly glacial pace of a television show about a guy in green leather who takes down bad guys with a bow.

However, the episode also may benefit from the decision to replace the flashbacks to the island, which have served little purpose since Feb. 13’s “The Odyssey,” with flashbacks to the birth of the Undertaking five years ago, shedding light on the plot, and the roles played by the Queens and Frank Chen. Beyond the requisite exposition, the scenes provide Robert Queen (played again by Jamey Sheridan) with some much-needed character development. He’s still the philanderer has was previously portrayed to be, but here we see him as troubled by his hand in the accidental death of a corrupt politician, and determined to stop Malcolm Merlyn’s insane plan to destroy the Glades and everyone who lives there. Of course, Robert is exposed as terribly naïve, as not only does he believe he can block Malcolm simply by buying up real estate in Starling City’s worst neighborhood, but he turns to Frank Chen for help.

Some things about the flashbacks, which lead to Robert and Ollie’s departure on the yacht, nicely synching up with events on the island:

• For an evil plot to destroy the Glades in a way that will look like a natural disaster, “the Undertaking” suddenly doesn’t sound so sinister when you realize Malcolm uses the term as a synonym for project or venture and not, say, a reference to funeral preparations.
• Moira’s betrayal of Frank now seems like poetic justice considering that he revealed Robert’s plans to Malcolm and planted the bomb on Queen’s Gambit.
• We’re expected to believe each member of this secret cabal of Starling City’s wealthiest citizens has a personal grievance against the Glades? I don’t buy that all of these people, living in their mansions and penthouses and protected by security, have lost something near and dear to that neighborhood.
• Oliver really was a dick before the shipwreck, wasn’t he? While Laurel is floating the idea of the two of them moving in together, he’s cheating on her with her sister (he even calls Sara at the dock, warning her to circle the block because Laurel has appeared to say goodbye).
• Oliver’s wig! As bad as the island hairpiece is, it’s nothing compared to this one, which looks as if it were at some point intended for a Ken doll.

But back to the present, where following the Hood’s takedown of a shady accountant who works for Starling City’s worst white-collar criminals, Felicity and Oliver discover a key link to Walter’s abduction: a money transfer on the date of his disappearance. That in turn leads them to Dominic Alonso, kidnapper and owner of an underground casino, which Felicity must infiltrate in a pretty shaky scheme to get caught counting cards so she can be hauled into the office to plant a listening device. Without Diggle, who’s still smarting because Ollie chose Laurel over him (come on, that’s what it really comes down to!), Team Vigilante may not be the best strategists.

Amazingly, everything goes as planned, as Alonso lectures Felicity and bans her from the casino … before detecting that she’s wearing an earpiece, as cheats frequently do to communicate with their accomplices. Their rickety plan exposed, Ollie comes crashing in, taking out security, dealers and much of the furniture before wringing out of Alonso that, yes, he played a part in the abduction of Walter, who was presumably shot by his captors. Ollie probably should’ve just taken this approach in the first place, rather than putting Felicity in danger, but that might’ve left the episode about five minutes short.

Concocting a flimsy story about information provided by one of Diggle’s FBI buddies, Ollie mournfully delivers word of Walter’s death to Thea and his mother, who flies into a rage that propels her to Malcolm who, with a phone call, provides Moira with live-video evidence that he kept his word: Walter is very much alive. With that call, everything begins to unravel, as Ollie hears the entire exchange using one of those eavesdropping arrows attached to the outer wall of Malcolm’s office.

Star Stephen Amell, whose range pretty much has been limited to “goofy grin” and “steely determination,” pulls off a terrific devastated son has he’s left reeling by the revelation that his mother was not only compliant in Walter’s abduction but also involved with Malcolm Merlyn in the byzantine plot involving the Glades. (Bruce Wayne, if he exists in the Arrow universe, clearly faces no competition for the title of “World’s Greatest Detective,” as Oliver & Co. keep stumbling upon critical information completely by accident.)

Using Malcolm’s phone records, Felicity quickly learns that Walter is behind at a remarkably high-security tenement in Bludhaven, a city so decrepit and crime-riddled that nobody notices when a rundown building has more armed guards than the White House. And that’s a good thing, really, because it leads to the most remarkable fight scene of the season, as Oliver parachutes (!) in to the structure, taking out at least a dozen henchman without breaking a sweat. It’s a beautifully choreographed, and delightfully violent, sequence that ends with the rescue of Walter and his return to Starling City.

At the hospital, Oliver must not play along as his tearful mother welcomes back her husband but face a seemingly joyful Malcolm, who deftly questions whether Walter was able to identify his abductors. Ollie, barely able to contain his anger, assures his newly discovered nemesis that those responsible will get what’s coming to them.

Rattled by these events, Ollie confesses to Laurel that he’s still in love with her before finally apologizing to Diggle, admitting that he was right about Moira. And, even as the truck carrying Malcolm’s mysterious Glades-destroying device makes its way to Starling City, Oliver tells Diggle that he needs his help to stop prevent the Undertaking.

This week’s DC Comics connections

• Bludhaven again, but that’s an easy one.
• In a flashback, Moira Queen mentions a Ted Kord fundraiser, a reference to the second Blue Beetle (created by Steve Ditko).
• The machine Malcolm Merlyn plans to use to destroy the 24-block area of the Glades in an earthquake is called the Markov Device, an apparent nod to Brion Markov and/or his half-sister Tara, who as the costumed Geo-Force and Terra possessed the ability to manipulate the earth.
• Making her case to Ollie, Laurel in flashback mentions that her friends Ray and Jean have moved in together, which may be a reference to Ray Palmer (The Atom) and Jean Loring.