You’re in the clear. Fiction synopses follow the “literary present” axiom and are written in present tense, but it’s okay to break away, just for a sentence or two, to mention a past event that somehow informs the present happenings:
- Sarah hates jocks, who always stop and hassle her, wondering if she’s the girl who almost burned down the gym last year. Luckily, Sarah’s brother saved the gym—and her along with it. He even saved the spirit banner from the flames. Now, on the anniversary of the fire, her brother gets to strut down the hall like some super hero while she has to hide behind her locker door until the bell rings.
As long as you keep past tense breakaways short, sweet, and rare, no one will be confused or distracted.