Help me track down a short story about a pursuit across time-rates?

This was in an anthology from way back in the 60s or 70s when I was just getting into SF - I've no idea who the author was.

One man pursues another as he slips across different time rates - the only detail I can remember is something towards the end about seeing "by the grey light of gravity". Not much to go on, I know, but it might jog someone's memory!