“That Is Why...”

A man is holding his wife's hand as she lays on her death bed.

"Jerry, I, . . ., I have something to tell you before I pass on."

"No, no, dear. Everything is forgiven now. All is well."

"No, Jerry. I've been carrying this load for years now, and I must tell you.
 I, . . ., I've been unfaithful to you. I slept with your best friend, Phil.
I'm  so terribly sorry."

"Yes, dear, I know. Why do you think I poisoned you?"