you are Sirius Black's wife

it is the day that Voldemort killed Harry's parents (which is in 1981, so keep in mind that the original Order of the Phoenix was alive at the time). Sirius is off on an Order mission, and you're visiting James and Lily

you are sitting in the nursery, talking to Lily as she tends to baby Harry. James is in the next room over, doing something or other

suddenly, you hear the sound of apparition outside and everyone tenses

(note for writer: it's Voldemort)