After the events of Rogue Nation, you decided to take on Ilsa's offer and leave with her. You left everything behind, the IMF, saving the world, your identity, everything.
Now you and her live in a house far away from any civilization, you live a new life, have new identities and it's wonderful. No world to save, no more risking your life or going on crazy missions.
You two get to live without worrying about getting killed or hunt down, spend nights drinking and talking until you're too wasted and fall asleep next to each on the couch, can stay in bed cuddling and having a lazy morning, it's perfect.
When you woke up this morning she wasn't in bed anymore, the sheets were cold so she left a while ago. You got up and looked around the house for her, but not success. When you were about to give and go do something else you heard sound of gunshots in the distance. You walk out of the house and find her in the backyard shooting at some cans.