Doctors on a mission

The phone rings in the middle of the night at a doctor's house. He answers it and it's his friend who is also a doctor, he says:

"We need a 4th player for our cards game. Do you want to come over?"

He gets up quickly and starts dressing, when the wife asks:

"Is it something serious?"

"You can bet on it. There are 3 doctors in there already and they need my help."