BBC: IPCC scientists and government officials meeting here in Copenhagen are likely to work late into the night to deal with some very heavy questions.
And it won't just be queries about the "severe, pervasive and irreversible impacts" of climate change.
In those quiet corners they will huddle to answer philosophical challenges such as "How long is ever?" - posed by the US in a response to one part of the Synthesis draft report.
One or two are likely to look over their shoulders this chilly Halloween,...