Who let the doctor in?

Rating: Null/10 (27 August 2014)

Carol is running into the house, after seeing an "MD" license plate, she greets the doctor and finds out who he is and why he is there. At the same time the grandmother walks in with groceries and says "I'm back".
I have to wonder who let the doctor in. Why would the son allow a strange man to come into his home and exam him, or did the grandmother let the doctor in and then go grocery shopping? If so, why would she leave the boy alone with a stranger? It just doesn't make sense to me, after seeing how protective Carol and the Grandmother were about Spencer.