(Edit: Whilst finding out if this opening was good, I found the PERFECT OPENING - The Colle-Zukertort System, image 2. The Stonewall Attack is image 1.)
The Stonewall Attack is an aggressive opening where white tries to build a powerful dark-squared pawn presence and control the light squares with the minor pieces. It is like The Colle-Zoltanowski System( just the london system without moving the dark squared bishop to f4) but there is also a pawn on f4.
When black plays c5 white often plays c3, providing the escape square c2 for the bishop on d3.
The main middlegame plan is to place a knight on e5 and if black plays c4 to lock the centre then place your bishop on c2 then play aggressive moves like g4 because the centre is locked.