Kolymsky Heights by Lionel Davidson

Kolymsky Heights. A Siberian hell lost in endless night: the perfect setting for an underground Russian research station. It's a place so secret it doesn't officially exist; once there, the scientists are forbidden to leave. But one scientist is desperate to get a message to the outside world.

So desperate, he sends a plea across the wildness to the West in order to summon the one man alive capable of achieving the impossible ...