Edna

Jim and Edna were both patients in a mental hospital.

One day while they were walking past the hospital swimming pool, Jim suddenly jumped into the deep end. He sank to the bottom of the pool and stayed there.

Edna promptly jumped in to save him.  She  swam to the bottom and pulled Jim out.  When the medical director became aware of Edna's heroic act he immediately ordered her to be discharged from the hospital, as he now considered her to be mentally stable. 

When he went to tell Edna the news he said, "Edna, I have good news and bad news. The good news is you're being discharged; since you were able to rationally respond to a crisis by jumping in and saving the life of another patient, I have concluded that your act displays sound mindedness.

The  bad news is, Jim the patient you saved, hung Himself with his bathrobe belt in the bathroom. I am so sorry, but he's dead." 

Edna replied, "He didn't hang himself, I put him there to dry.  Now... How soon can I go home?"