Rafael van der Vaart scored the only goal of the game at Vicarage Road to send Tottenham into the fifth round of the FA Cup at the expense of an impressive Watford side.
The Premier League high-flyers had barely mustered an attack before they took the lead when van der Vaart picked up Kyle Walker's pass three minutes before the interval and rifled home from 25 yards.
Marvin Sordell had previously missed a brace of chances for the home side and Prince Buaben also went close while 18-year-old Irish midfielder Sean Murray impressed in only his second game for the Hornets.
The hosts were almost level on 49 minutes when Murray broke into the box but Carlo Cudicini tipped his shot onto the post and Troy Deeney sent the follow-up wide of an open goal.
That brought Spurs briefly to life and Scott Loach had to push a Kyle Walker header onto the roof of the net at the other end before and van der Vaart curled a sweetly-struck shot onto the crossbar.
Watford cranked up the pressure again on 70 when John Eustace headed a corner onto the upright and Buaben and Mark Yeates both had chances but they could not find an equaliser despite their industry.
In the night's other game, Marouane Fellaini headed the winner as Everton battled back from a goal down to defeat Fulham 2-1.
Everton fell behind when Danny Murphy slotted a 14th-minute spot-kick home after Johnny Heitinga was adjudged to have handled, but the aggrieved hosts nearly hit back quickly when Shane Duffy nodded over.
Tim Cahill's header then drew a decent stop from David Stockdale, but Fulham's keeper could not hold Everton at bay as Stracqualursi nodded in Landon Donovan's cross just before the half-hour mark.
The Cottagers gave a reminder of their threat when Clint Dempsey headed over in the second half, but Everton looked the more likely scorers and Stockdale had to rush out to deny Denis Stracqualursi.
Quick thinking from Phil Neville created the winner as his swift free-kick released Donovan whose cross was nodded into the corner by Fellaini before Cahill's header hit the bar late on.