The first thing to do here is to walk past the trainers and tall grass to the wooden bridge, where Steven is. He will use his Devon Scope to reveal a wild Kecleon which immediately attacks. This is a good time to catch one if you haven't already, but don't worry if you don't catch it - they can be found in tall grass on this route (though they are admittedly rare). After the battle ends, he gives the Devon Scope, which will allow you to scare off the Kecleon blocking access to Fortree City's Gym. Upon returning to the area, if you keep to the north, you'll find two familiar faces.