An explosive 10-minute spell either side of half-time saw Larne grab four goals and book their place in the semi-finals of the Toals County Antrim Shield.
Two goals before the break and two more just after it for Tiernan Lynch's side saw them tear Crusaders apart in some style.
To make matters worse for Stephen Baxter's side, they saw three former Seaview stars on the scoresheet in the form of Marty Donnelly, Andy Mitchell and Ronan Hale.
Both sides made a handful of changes from their Shield outings on Saturday, but it was a player who had already made his debut for the visitors who came closest to opening the scoring on 15 minutes.
Jordan Forsythe did well to make time for himself on the right flank and his cross was headed inches wide by recent signing Adam Lecky.
Despite Crusaders starting the game well and on the front foot, it was Larne who were next to threaten midway through the half. Mark Randall's side-footed effort, after a Donnelly corner, was stopped on the line by a combination of goalkeeper Ger Doherty and two of his defenders.
The opening goal arrived seven minutes before the break, with an exquisite finish from Donnelly.
Former Crusaders forward Ronan Hale saw his initial acrobatic effort blocked on the edge of the box and the ball broke to Donnelly. The little winger took a touch before despatching it into the top left corner, leaving Doherty with no chance.
The second arrived on 43 minutes. This time, Randall's in-swinging corner from the left was met by the head of Albert Watson, who nodded it in at the back post.
Despite the introduction of Paul Heatley from the bench at half-time, things got worse for the Crues when Randall was upended in the box.
After waving away initial protests, referee Tony Clarke then pointed to the spot.
Another former Crusaders player, Mitchell, slotted home the resulting spot-kick to make it 3-0 on 48 minutes.
Three minutes later and Larne continued to run amok. This time Donnelly turned provider and his slide rule pass set Ronan Hale away inside the box, and he simply fired across Doherty for No.4.
The closest the visitors came to pulling a goal back was when, with 18 minutes left on the clock, Ross Clarke cut in from the right flank and let fly from 25 yards - however, his drive came back off the base of the post.
Tomas Cosgrove brought a good save from Doherty late on, as Larne held on comfortably for the win.
Larne: Devlin, Kelly, Watson, Robinson, Sule, Randall (Herron, 74), Hale (McDaid, 80), Donnelly ('90 Murr), A Mitchell, Wade-Slater, Cosgrove
Unused subs: C Mitchell, Lynch, Murr, Hughes
Crusaders: Doherty, Hegarty (Heatley 46), Wilson, Hale, Caddell, Forsythe, Lecky (McGonigle 76), Ruddy, Brown, Thompson, Clarke (Owens 76)
Unused subs: O'Neill, Lowry , Cushley, O'Rourke
Referee: Tony Clarke (Portadown)
Man of the match: Marty Donnelly
Match rating: 8/10