Andrew Haigh’s “Lean on Pete” is an elegantly made film with shimmering cinematography and heartbreaking performances topped by Charlie Plummer. This beautifully edited movie about a boy in search of his mother with the aid of the horse Pete, feels like a tone poem. The slow pace sticks to your ribs as you ingest Portland and Wyoming through Charlie’s eyes. Andrew Haigh is on the fast track to become a treasured director after his vastly different previous films 45 Years and Weekend.