Another pure red flag in Synastry! If your Pluto is making contact with your partner’s Mars (or vice versa), that too via a square, then we’d strongly suggest you keep out of this association.
When the two of you meet, the sexual attraction will be deep and irresistible. But, this square does not guarantee a long time association. Pluto is a dark planet, and Mars is confrontational by nature.
Both Pluto and Mars seek power over each other. Power struggles will reign supreme in this combination, and thus, conflicts will become an integral element of your relationship. Surely this isn't the tango you’d prefer doing it.
Emotional manipulations, physical injury, and violence could also manifest as the attraction between the two of you will start wearing out.