You have a project due in one hour but a more important emergency that affects business needs to be fixed immediately, what do you do?

I will shift from project to business need as the business is always the priority for us. But before shifting, I would ensure to convey the same to my manager and will also raise the flag that while I am doing this the project will get hampered. So that they can work on finding the way to improve the project as well or can assign that to someone else. If nothing is doable, then they or maybe I can raise it to the client.