Save past GNU screen output to a file

I have had a GNU screen session running for days. I find myself in the situation that I need to save the terminal contents (which I can scroll up to see) into a file. Is this possible? I estimate it to be below 5000 lines. I found a way to set up screen to log *future* output to a file. But in this case, I need to also save past output (or as much of it as is present).