Harry Potter and the Starship Enterprise

A crossover with Classic StarTrek. Here Dr. Christine Chapel is Harry's godmother (his mother's best friend) and Dumbledore's grand-daughter (he and McGonagall are married here) and Christine was once engaged to Sirius, Harry's godfather. HP universe is canon except for being set in 23rd century.

Christine and Harry get to know each other ... among other things.

Christine meets with Spock and tells him the situation, her true background and what he should expect as her informer.

There is an Order meeting to decide the best course of action; in the midst of it Christine has a flashback to the last time she saw Sirius. Two days later, there is a private talk between all concerned at the Burrow. At the end of same, Harry asks her to tell him what happened at the Order meeting.

Christine eavesdrops on Harry and his friends' discussion about their quest, then decides to have a talk with Ginny and ends up doing some discreet matchmaking in order to bring her and Harry back together.

Christine and Harry go to Diagon Alley and she basically buys it out, getting things for him and making up for sixteen years of lost time. They also discuss Spock's news about the Dark side's plans and what to do about it, among other things.

Christine decides to attempt to record the functioning of the veil in the Department of Mysteries which Sirius disappeared through in hopes that Spock will be able to decipher its operation (and recreate the interdimensional portal) to hopefully locate Sirius.

Christine meets with Harry and his friends and discusses the latest developments regarding the Department of Mysteries.

Christine and the other Order members implement their agreed-upon plan to protect Harry and his classmates from attack by Dark forces while on the way to Hogwarts.

Harry goes with Christine and Spock to look for Sirius when they arrive at the planet where he is believed to be.

Sirius settles back in, rejoining the Order and reacquainting himself with both Harry and Christine, among others.

Shortly after Arthur Weasley meets Spock, they all discuss what to do for the coming battle with Voldemort and company.

Sirius and Christine are reunited romantically after Spock leaves; shortly thereafter, the row between Remus and Harry takes place and Sirius angrily confronts his godson.