Fifty metres to his right, he noticed a patch of forest where the trees were more widely spaced and the trunks were noticeably thinner than the majority of trees in the forest. He slipped to a new vantage point and studied the lie of the land from behind the bole of a tree.
Nothing moved. But his senses told him this would be the place. He eased away from the tree and slipped forward for another five metres, then went behind another tree, his eyes never leaving that area where the trees thinned.
He had actually raised his right foot to step out from behind cover when he spotted a brief flicker of movement and froze instantly. He waited, foot partially raised, eyes boring into the grey ranks of trees, waiting to see if the movement might be repeated.
Then he saw them. And once he’d picked them out, he wondered how he’d ever missed seeing them in the first place. Although he had to admit that the dull purple cloaks blended well into the shadows of the forest.
He smiled grimly. It was the movement that had betrayed them. Move and you’re almost certain to be seen, Halt had told him over and over as they had practised.

Halt's Peril, Chapter 22