When she’s excited, Iris wags her whole body. Even the nylon tunnel can’t contain her delight. The black Lab disappears into the tunnel, and her joy becomes sound: slap, slap, slap, tail on tube. You’d never know it’s dark in there. Rusty, a smiling yellow Lab, and Ruger, a German Shepherd whose smile is hidden by the large toy in his mouth, can’t wait for whatever comes next. That turns out to be the arrival of Falco and his owner, Jason Rogers.