There's a lot riding on tonight's replay in Falkirk, with a televised home tie against Hearts the reward for the victors.
"It could stabilise the club for another couple of years," says Arbroath manager Dick Campbell of the money at stake.
He must do without on-loan Hearts striker this evening since he wasn't signed before the initial game and he obviously won't be available if they get through.
Master v apprentices
Falkirk v Arbroath (19:45)
Falkirk are just one point off the top of League One and haven't lost a game since Lee Miller and David McCracken took over as rookie co-managers in November.
But they're up against the best part-time team in Scotland this evening, with Arbroath holding their own in the Championship under the shrewd guidance of the vastly experienced Dick Campbell.
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Lee Miller and David McCracken have made a big impression at FalkirkImage caption: Lee Miller and David McCracken have made a big impression at Falkirk
'We can't afford to lose our best assets'
Hibernian v Dundee United (19:45)
Dundee United boss Robbie Neilson asserts the 'not for sale' message when asked about the future of striker Lawrence Shankland.
"It will be difficult," he says of the tie. "Hibs are a strong team but we fought back well last time and we come here with confidence. We have the qualities to hurt them.
"The players understand the magnitude of the game. This is the level we want to be playing at week-in, week-out.
"Lawrence is a very level headed human being. He's not getting carried away. There are no plans to sell him this month, with promotion our priority. We can't afford to lose our best assets, so I'll be camping outside his house making sure he doesn't go anywhere. It might be a different story in the summer."
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Lawrence Shankland takes in the surroundings at Easter RoadImage caption: Lawrence Shankland takes in the surroundings at Easter Road
Goalless at Gayfield
Falkirk v Arbroath (19:45)
It wasn't quite so entertaining at Gayfield, with the teams drawing a blank.
Arbroath had the best of the first half but Falkirk were on top after the break, with Derek Gaston making a couple of vital stops.
Tannadice thriller ends all square
Hibernian v Dundee United (19:45)
What happened last time? These two served up a four-goal cracker at Tannadice, with Hibs twice taking the lead and the Championship leaders twice hitting back.
Christian Doidge and Martin Boyle were on target with excellent goals for the visitors that day, while Lawrence Shankland tucked away the only chance that came his way and substitute Louis Appere curled in a beauty to earn United this replay.
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Louis Appere watches his curling strike on its way into the back of the net, via the base of the postImage caption: Louis Appere watches his curling strike on its way into the back of the net, via the base of the post
Shankland not moving on this month
Hibernian v Dundee United (19:45)
Jane Lewis
BBC Sport Scotland at Easter Road
There a scouts are here tonight from Sheffield United, Stoke City and Coventry but Dundee United manager Robbie Neilson insists the club will not entertain any bids for top-scorer Lawrence Shankland in January.
Hibs boss Ross looks for high tempo
Hibernian v Dundee United (19:45)
Hibernian head coach Jack Ross has been talking to BBC Sportsound, joking that he hopes someone comes in with an offer for United striker Lawrence Shankland before kick-off...
"It's important we play with a good pace and tempo because we created a lot of chances that way in the first tie.
"Stephane Omeonga is ineligible, so Steven Whittaker, who was good at Tannadice and has a lot of quality, comes in.
"It's our fourth game in 10 days so we need a freshness in attack. Scott Allan is back and Florian Kamberi drops to the bench, but he will have a part to play this evening.
"We're a little light on numbers and we're working hard to bring in players but we haven't been successful yet."
Shankland keeps banging them in...
Hibernian v Dundee United (19:45)
Lawrence Shankland found the net in the first tie and the prolific striker was at it again on Saturday, scoring deep in injury time to earn Dundee United a 1-1 draw at home to Morton.
Robbie Neilson's side now lead the Championship table by a whopping 18 points.
The 24-year-old has banged in an incredible 27 goals in 28 outings this season, including one for Scotland against San Marino.
Tap-ins, left foot, right foot, headers, screamers. He got them all in his repertoire.
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Lawrence Shankland scores at the death at home to Morton on SaturdayImage caption: Lawrence Shankland scores at the death at home to Morton on Saturday
There's no TV coverage of tonight's game in Edinburgh, which makes these text updates a little trickier than usual.
By a quirk of fate both replays will determine BBC Scotland's live television offerings for the next round.
Should Hibs prevail, their match against BSC Glasgow will be on Sunday, 9 February (12:00 GMT), with the tie scheduled for two days earlier (19:05) if United win through.
Hearts' fifth-round trip to Falkirk or Arbroath will be shown on Saturday, 8 February at 19:20.
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Where and when will the BBC cameras be required next?Image caption: Where and when will the BBC cameras be required next?
Fifth round draw reminder
Inverness Caledonian Thistle v Livingston
Clyde v Celtic
BSC Glasgow v Dundee United or Hibernian
St Mirren v Motherwell
Ayr United v St Johnstone
Aberdeen v Kilmarnock
Hamilton Academical v Rangers
Arbroath or Falkirk v Heart of Midlothian
Ties to be played on the weekend of Saturday 8 February.
Let's go round again
We've got two Scottish Cup fourth round replays for you this evening.
BBC Sportsound will be providing live radio commentary from Hibs v Dundee United at Easter Road, while we'll get updates from the Falkirk Stadium, where Arbroath are the visitors.
Live Reporting
Colin Moffat
All times stated are UK
High stakes with Hearts up next
Falkirk v Arbroath (19:45)
There's a lot riding on tonight's replay in Falkirk, with a televised home tie against Hearts the reward for the victors.
"It could stabilise the club for another couple of years," says Arbroath manager Dick Campbell of the money at stake.
He must do without on-loan Hearts striker this evening since he wasn't signed before the initial game and he obviously won't be available if they get through.
Master v apprentices
Falkirk v Arbroath (19:45)
Falkirk are just one point off the top of League One and haven't lost a game since Lee Miller and David McCracken took over as rookie co-managers in November.
But they're up against the best part-time team in Scotland this evening, with Arbroath holding their own in the Championship under the shrewd guidance of the vastly experienced Dick Campbell.
'We can't afford to lose our best assets'
Hibernian v Dundee United (19:45)
Dundee United boss Robbie Neilson asserts the 'not for sale' message when asked about the future of striker Lawrence Shankland.
"It will be difficult," he says of the tie. "Hibs are a strong team but we fought back well last time and we come here with confidence. We have the qualities to hurt them.
"The players understand the magnitude of the game. This is the level we want to be playing at week-in, week-out.
"Lawrence is a very level headed human being. He's not getting carried away. There are no plans to sell him this month, with promotion our priority. We can't afford to lose our best assets, so I'll be camping outside his house making sure he doesn't go anywhere. It might be a different story in the summer."
Goalless at Gayfield
Falkirk v Arbroath (19:45)
It wasn't quite so entertaining at Gayfield, with the teams drawing a blank.
Arbroath had the best of the first half but Falkirk were on top after the break, with Derek Gaston making a couple of vital stops.
Tannadice thriller ends all square
Hibernian v Dundee United (19:45)
What happened last time? These two served up a four-goal cracker at Tannadice, with Hibs twice taking the lead and the Championship leaders twice hitting back.
Christian Doidge and Martin Boyle were on target with excellent goals for the visitors that day, while Lawrence Shankland tucked away the only chance that came his way and substitute Louis Appere curled in a beauty to earn United this replay.
Shankland not moving on this month
Hibernian v Dundee United (19:45)
Jane Lewis
BBC Sport Scotland at Easter Road
There a scouts are here tonight from Sheffield United, Stoke City and Coventry but Dundee United manager Robbie Neilson insists the club will not entertain any bids for top-scorer Lawrence Shankland in January.
Hibs boss Ross looks for high tempo
Hibernian v Dundee United (19:45)
Hibernian head coach Jack Ross has been talking to BBC Sportsound, joking that he hopes someone comes in with an offer for United striker Lawrence Shankland before kick-off...
"It's important we play with a good pace and tempo because we created a lot of chances that way in the first tie.
"Stephane Omeonga is ineligible, so Steven Whittaker, who was good at Tannadice and has a lot of quality, comes in.
"It's our fourth game in 10 days so we need a freshness in attack. Scott Allan is back and Florian Kamberi drops to the bench, but he will have a part to play this evening.
"We're a little light on numbers and we're working hard to bring in players but we haven't been successful yet."
Shankland keeps banging them in...
Hibernian v Dundee United (19:45)
Lawrence Shankland found the net in the first tie and the prolific striker was at it again on Saturday, scoring deep in injury time to earn Dundee United a 1-1 draw at home to Morton.
Robbie Neilson's side now lead the Championship table by a whopping 18 points.
The 24-year-old has banged in an incredible 27 goals in 28 outings this season, including one for Scotland against San Marino.
Tap-ins, left foot, right foot, headers, screamers. He got them all in his repertoire.
Saints sign up McCart
The show goes on
Falkirk v Arbroath (19:45)
Falkirk's artificial pitch was given a dusting of snow last night but it was quickly dealt with.
LINE-UPS at the Falkirk Stadium
Falkirk v Arbroath (19:45)
Falkirk: Mutch, Doyle, Dixon, Buchanan, Durnan, Gomis, Telfer, Connolly, McManus, Miller, Sammon.
Substitutes: Bell. McShane, Leitch, Todd, De Vita, McMillan.
Arbroath: Gaston, Thomson, Hamilton, Little, O'Brien, Virtanen, Whatley. McKenna, Linn, Donnelly, Stewart.
Substitutes: Gold, Swankie, Kader, Murphy, Chalmers, Jamieson.
LINE-UPS at Easter Road
Hibernian v Dundee United (19:45)
Hibernian: Marciano, James, Jackson, Hanlon, Stevenson, Whittaker, Newell, Allan, Boyle, Horgan, Doidge.
Substitutes: Bogdan, McGregor, Gray, Kamberi, Hallberg, Murray, Gullan.
Dundee United: Siegrist, L Smith, Connolly, Reynolds, Robson, Powers, Butcher, Harkes, Pawlett, Appere, Shankland.
Substitutes: Deniz, Sporle, McMullan, Sow, Glass, King, Watson.
TV cameras will follow the winners
There's no TV coverage of tonight's game in Edinburgh, which makes these text updates a little trickier than usual.
By a quirk of fate both replays will determine BBC Scotland's live television offerings for the next round.
Should Hibs prevail, their match against BSC Glasgow will be on Sunday, 9 February (12:00 GMT), with the tie scheduled for two days earlier (19:05) if United win through.
Hearts' fifth-round trip to Falkirk or Arbroath will be shown on Saturday, 8 February at 19:20.
Fifth round draw reminder
Inverness Caledonian Thistle v Livingston
Clyde v Celtic
BSC Glasgow v Dundee United or Hibernian
St Mirren v Motherwell
Ayr United v St Johnstone
Aberdeen v Kilmarnock
Hamilton Academical v Rangers
Arbroath or Falkirk v Heart of Midlothian
Ties to be played on the weekend of Saturday 8 February.
Let's go round again
We've got two Scottish Cup fourth round replays for you this evening.
BBC Sportsound will be providing live radio commentary from Hibs v Dundee United at Easter Road, while we'll get updates from the Falkirk Stadium, where Arbroath are the visitors.