Leicester produced a superb second-half showing to advance to their ninth consecutive final with a 33-16 win over Harlequins.
The visitors showed impressive composure and control in the opening 40, holding their nerve at a ground where Leicester have never lost a Premiership semi-final.
Leicester though were spurred on by Vereniki Goneva's try before half-time, bursting out of the blocks in the second half to score tries through Niall Morris, Tom Croft and Mathew Tait.
Flood and Evans traded early penalties before the visitors' scrum laid down a marker, squeezing the Leicester front row out of shape to win a penalty and take a 6-3 lead.
A weary-looking surface at Welford Road continued to cut up following a burst of heavy showers before kick-off. Favourable conditions for Leicester - but it was Harlequins who looked the more composed side early on.
Leicester's best efforts continued to be thwarted, Luke Wallace ably filling in for Chris Robshaw at the breakdown with a crucial turnover within his own 22.
The net result was the deepest of touchfinders from Nick Evans, Harlequins positioned five metres out from the Leicester line. They nearly capitalised; some brilliant sharp-thinking from Croft doing enough to keep Danny Care out of a certain score in the corner.
It was Harlequins' driving maul, not Leicester's, which began to dominate the first half - leading to a simple penalty opportunity for Evans in front of the sticks to stretch the visitors lead to 9-3.
Leicester turned to their captain for inspiration and it was Flood's smart grubber kick which forced Care to scramble and handed the Tigers a platform. With the maul rumbling, Leicester looked for width but settled for three points.
Despite the high level of intensity, this was a not a match without great skill and Harlequins produced some outstanding continuity and handling but were unable to add more points before the interval.
Leicester had no such problem - Goneva scorching down the outside and bouncing off Tom Williams to go in under the posts from 40 metres out, swinging the momentum.
Wallace's ill-advised chip over the top then sent Harlequins right back to defending in their own 22 after the break, Leicester knowing a try would open up a very difficult gap. It wasn't to be, Goneva knocking on.
With conditions continuing to worsen under the Leicester drizzle, Harlequins searched for a territorial advantage - any advantage as Leicester pinned them back in their own half.
Their fortunes then took a downturn as Care was sin-binned for a deliberate knock-on, a call that looked harsh on the England scrum-half. Flood failed to add further damage with the resulting penalty kick.
Leicester though continued to probe and prod, a Flood grubber kick running too deep for the paws of Croft to touch down.
With Harlequins' penalty count continuing to rise, Leicester were afforded a bounty of field position and penalty opportunities, Flood successfully stretching the gap with an easy penalty.
The intensity then proved too much - Manu Tuilagi hammering his way into space down the left-hand side after Tait's initial break, finding Morris on his inside for the Irishman to race away for Leicester's second try.
Harlequins were restored to a full compliment but the damage had been done, the champions conceding ten points in the time Care was in the bin.
The result was then sealed thanks to more magic from Croft. Excellent in defence earlier on, he hit the accelerator and had far too much for Wallace, Evans and finally Karl Dickson to score in the corner at breathtaking pace.
Perhaps the only other player on the field as outstanding as Croft was Tait, the former England back deemed by many to be unlucky not to tour Argentina next month scampering in for Leicester's fourth and named Man of the Match.
Harlequins were out of it but not incapable or raising some smiles, Ross Chisholm crossing for a classy try after Williams' initial burst on the switch.
This though was Leicester's day - having weathered the early storm and then delivered a flurry of punches in the second half as Croft and Tait excelled. They await Saracens or Northampton at Twickenham.
Tries: Goneva, Morris, Croft, Tait
Cons: Flood 2
Pens: Flood 3
Pens: Evans 3
Yellow Card: Care
Leicester: 15 Mathew Tait, 14 Niall Morris, 13 Manusamoa Tuilagi, 12 Anthony Allen, 11 Vereniki Goneva, 10 Toby Flood (c), 9 Ben Youngs, 8 Jordan Crane, 7 Julian Salvi, 6 Tom Croft, 5 Geoff Parling, 4 Graham Kitchener, 3 Dan Cole, 2 Tom Youngs, 1 Logovi'i Mulipola.
Replacements: 16 Rob Hawkins, 17 Fraser Balmain, 18 Martin Castrogiovanni, 19 Steve Mafi, 20 Thomas Waldrom, 21 Sam Harrison, 22 George Ford, 23 Matt Smith.
Harlequins: 15 Mike Brown 14 Tom Williams, 13 George Lowe, 12 Tom Casson, 11 Ugo Monye, 10 Nick Evans, 9 Danny Care, 8 Nick Easter (c), 7 Luke Wallace, 6 Maurie Fa'asavalu, 5 George Robson, 4 Olly Kohn, 3 James Johnston, 2 Joe Gray, 1 Joe Marler.
Replacements: 16 Rob Buchanan, 17 Mark Lambert, 18 Will Collier, 19 Charlie Matthews, 20 Tom Guest, 21 Karl Dickson, 22 Ben Botica, 23 Ross Chisholm.
Referee: Greg Garner
Assistant referees: Stuart Terheege, Gordon Goodliffe
Television match official: Geoffrey Warren
Timekeeper: David Hudson
Assessor: Ed Morrison
by Ben Coles