Motherwell's first-half demolition of St Johnstone at Hampden took the Fir Park side to their first Scottish Cup final in 20 years following their 3-0 triumph.
Skipper Stephen Craigan scored his first goal in five years in the fifth minute when he capitalised on a blunder by Saints keeper Peter Enckelman to head in a Tom Hateley corner.
Further goals before the break from Jamie Murphy and John Sutton ensured the Steelmen will return to the national stadium on May 21 to face either Aberdeen or Celtic who play at Hampden on Sunday.
Motherwell were ahead, thanks to a blunder by Enckelman after five minutes. The former Aston Villa keeper flapped at Hateley's corner from the left, allowing Craigan the easiest of tasks to head in from six yards and celebrate his first goal in five years.
Saints were immediately deflated and in the 14th minute their task was made all the more difficult when Murphy drove low past Enckelman after dribbling all too easily to the edge of the box, helped by Saints defenders Steven Anderson and Michael Duberry colliding with each other.
St Johnstone midfielder Murray Davidson flashed a shot from distance just over the Motherwell bar to give Derek McInnes' side some hope.
Then Hateley got his head in the way of Daniel Grainger's whipped-in free-kick and was happy to see the ball skip just wide of his own goal and behind for a corner.
But in the 38th minute the game was over when Sutton took a pass from Francis Jeffers and arced a shot from 30 yards over the hapless Enckelman and in to the net.
In the 51st minute there was a St Johnstone claim for a penalty when defender Dave Mackay's throw-in looked as if it might have come off the top of Keith Lasley's arm in the box - but referee Iain Brines was unimpressed.
In the 80th minute Davidson crashed a header off the bar after latching on to a Grainger corner and with that any slim hopes of an unlikely Saints comeback were gone.
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