Ireland now top the standings having won all three of their matches so far, and another victory against Scotland on Saturday would set up a showdown with fellow championship hopefuls England at Twickenham in the final game.
Here, Starsport take a look at what could happen this weekend.
Only one side can claim the 2018 title this weekend, and that's Ireland.
Scotland's only change from that 25-13 win over England in which the visitors were denied even a losing bonus point sees young Edinburgh full-back Blair Kinghorn handed his maiden Test start on the right wing due to a back problem suffered by Tommy Seymour.
In the tournament preview, there was a discussion that if a team can make it to Round 4 with their title chances still intact then it can be considered a reasonably successful tournament.
They can, but it's going to tough.
What do Ireland have to do to win the Six Nations this week?
If the Irish secure a bonus-point win over the Scots, England MUST do the same against France to keep things going to Twickenham. If we allow Ireland to muscle up they will grind us into the dirt, so we need to move them around when we have.
Depending on England's result they are then likely to need a bonus point win and huge margin of victory against Italy on the final day to claim the overall tournament. When you've only got two in your history, you'll take them when they come. "We had some really good stuff that went down the middle against Wales, but we had some good stuff on the edges with some of the best passes you will see in world rugby".
If a team loses but scores four tries and loses by less than seven points they will be awarded two points.
Former Ireland scrumhalf Tomas O'Leary believes that the prospect of completing their third ever Six Nations Grand Slam will be playing on the minds of the Irish team.
Check out the Six Nations table heading into this weekend's matches.