The mirror relents to Strange and Crozier follows after, the cold knocking the breath from his lungs as he steps on through to the other side.

They're back in the Arctic, out on the frozen Victoria Straight surrounded by tall pressure ridges and seracs. He can't see Terror or Erebus, nor any paths or any sign that they'd traveled through there before, but there's blood on the ice.

So, so much blood.

Surrounding himself and Strange are the bodies of five adult seals, bellies gutted and steam still rising from the fresh kill.

Crozier tenses. "I don't know this."