in hot pursuit
at someone's heels
on someone's heels
hard on someone's heels
hot on someone's heels

I didn't look back to see what was at my own heels.

A little man was at his heels as he walked in.

You have to be just a little bit down at the heels.

As he walked back to the big house, they followed at his heels.

She went through to the kitchen and found him at her heels.

He knew without looking that James was at his heels.

Dog at his heels as he went off down the road.

He could almost feel the wonder in the boy at his heels.

And all the time the dog ran with him, at his heels.

He went through the hall with the dog at his heels.