"Much hangs on the tides," van Hoek said. "We want a low tide in the night-time. And the weather must remain calm, so that we can row away from any pursuers during the hours of darkness. At sunrise the wind will come up, and then anyone who can see us will be able to catch us..." His voice trailed off to a mumble as he pondered these and other complications, which had seemed hardly worth mentioning when they had been developing the Plan, and now, like shadows at sunset, stretched out vast, vague, and terrifying.