I remember this pic, I read a few years ago. Buffy is a child and gets kidnapped by Drusilla, who takes her back to spike. If I remember correctly this fic had something with soulmates and eyes changing color when you met them for the first time, but I might be mixing things together. Either way, spike chooses not to kill Buffy, and he takes her back to Joyce and spends the next many years watching over her. It's not Every Letter That You Write Me, or Port In A Storm.

Hi anlohvilshoj,

It's without any doubt In Omne Tempus by Holly 😊

Summary: For a hundred years, William the Bloody has led a trail of bloodshed and chaos across Europe and the Americas. That all comes to an end when the woman he's devoted his existence to brings his mate to him in the guise of a late-night snack. A small girl with eyes of green and blonde hair. And suddenly, Spike is thrown into a world of color beyond the black and white, and his life is never the same.

Hannora
Oh, thank you!!