As it was impossible to take the ambulance into the dunes, it was left in the rear in charge of Jones, while the others threaded their way in and out the devious passages toward the front. They had covered fully a mile in this laborious fashion before they came upon a detachment of Belgian infantry which was lying in wait for a call to action. Beyond this trench the doctors and nurses were forbidden to go, and the officer in command warned the Americans to beware of stray shells.