Ponies and parachutes

Jo McKissock and her friend Joe are looking forward to all the riding they will get in the holidays on her uncle's Highland sheep farm, and to the local show which includes a gymkhana where along comes her strange Canadian cousin Chris, to sneer at them and apparently to stay for ever. As if there were not enough disturbance from him, there is a gang of payroll robbers supposed to be in the neighbourhood and everyone has to take spacial precautions. All in all it's a marvel that they come to take part, in no small way, in the paratroops' manoeuvres....