Anyone know of a radio drama about an advanced alien civilization visiting Earth (we don't know it's Earth until the end). Everything is deserted. They send down teams to investigate and one team accidentally engages the drive in a high speed underground shuttle that takes them into a tunnel and beneath a major city (NYC?). The mothership can't get to them. One member of the team is a different race, an organism that has an identical counterpart on the mothership. They are separate but are parts of a whole and communicate as one organism and it is from these special crew members that they finally get help and are rescued by the mothership. The captain on the mothership is able to locate them and blasts a hole down to retrieve them.
The planet (Earth) is soon to be destroyed by some catastrophe such as a colliding planet or the sun going nova. So they rush to find their team before the planet is destroyed and they stuck below and up on the mothership all are killed too.
The episode ends with the team being rescued and all escaping the dying planet just in time. Then scanning ahead and seeing thousands of ships in the distance, apparently the last inhabitants of the dying planet Earth who had already fled. It's a rag-tag fleet. The captain makes a joke at the end that perhaps they'll do just fine and be at their own level...in about a million years from now. It was produced in the 70s or 80s.