Teenager George Ford drove Leicester into a remarkable eighth successive Premiership final as Tigers ended Saracens' reign as English champions.
The 19-year-old, son of former England defence coach Mike Ford, kicked four penalties and a conversion after replacing ankle injury victim Toby Flood.
Ford's inclusion was the headline selection by Tigers, especially as they had named Flood on their official team sheet yesterday, but he did not let down a club in pursuit of its 10th league title.
In addition to his priceless points from the boot, Ford also created both Leicester tries through slick passing that cut open a Saracens defence renowned for its Scrooge-like quality.
Wing Alesana Tuilagi, on his final Tigers appearance at Welford Road before moving to Japan, touched down midway through the first half, while flanker Steve Mafi also crossed to thwart a Saracens side whose points came from five Owen Farrell penalties.
Leicester slumped to 11th in the Premiership after their first six games, of which they lost five, but 14 subsequent victories and a draw saw them climb to just one point behind regular season leaders Harlequins.
And it was Ford, current junior world player of the year, who showed admirable maturity to steer Leicester towards a Twickenham appointment with Quins on May 26.
England international Flood will probably return for the final, yet there can be no doubting Ford's contribution to Tigers during a season when he also kicked 16 points in their LV= Cup final victory over Northampton.
Saracens, despite leading 12-10 just before the break, were punished for their failure to convert a number of promising attacking positions into points.
And Leicester needed no second invitation to capitalise as fortress Welford Road once again lived up to its reputation for visiting teams.
Tigers' official explanation for Flood's absence was that he failed a late fitness test, while flanker Craig Newby took over from Julian Salvi (hamstring), who Leicester said was also a late cry-off.
Farrell lined up at outside centre for Saracens, with Charlie Hodgson wearing the number 10 shirt and young flankers Jackson Wray and Will Fraser also featuring as the visitors targeted a fourth successive victory on Leicester soil.
Farrell and Ford exchanged early penalties, but Saracens looked the most threatening side early on, and they should have posted a 12th-minute try.
Fraser made a superb touchline break before full-back Alex Goode found David Strettle, but although the England wing avoided Tuilagi's tackle, he lost control of the ball as he stretched for a one-handed touchdown.
Farrell then put Saracens back in front with a short-range penalty, yet Leicester bounced back midway through the half when Samoa international Tuilagi powered over for his 63rd Tigers try after a superbly-timed Ford pass.
Ford added the conversion, hoisting Leicester 10-6 ahead as Saracens suddenly found themselves in reverse gear, courtesy of Tigers cranking up intensity levels.
A third Farrell penalty cut the gap to a point, and then after he missed an angled strike, his fourth successful goal put Saracens 12-10 in front nearing the end of a ferociously-intense first period.
Ford, though, had the final say, displaying an unflappable temperament when he bisected the posts from just inside Saracens' half to secure a 13-12 interval advantage for Tigers.
Ford missed an early second half penalty, yet his response was both audacious and brilliant, slashing through Saracens' midfield defence and allowing Leicester to spin possession wide that ended with Mafi crossing.
Saracens breathed a collective sigh of relief when Ford drifted the conversion wide, but his successful penalty just three minutes later left the visitors more than a converted try adrift.
Farrell's fifth successful penalty ensured a gripping final quarter, but Tigers had more than enough left in the tank to cross the finishing line.
Saracens, despite the best efforts of workaholic forwards Schalk Brits, prop Matt Stevens and skipper Steve Borthwick, had to concede second best as Leicester began preparing for a familiar journey to Twickenham in two weeks' time.
And Ford's final penalty success five minutes from time meant Leicester could finally breathe easily, content that it was yet another case of mission accomplished in a major semi-final.