A 27-year-old home-health-care nurse thought she was doing her disabled patient a favor when she let him crash at her Northeast apartment early yesterday after an argument drove him out of his own home.

But instead of thanking her, the man allegedly raped her as she slept, police said.

Ernest Johnson, 50, of Frankford, told the victim he needed a quiet place to clear his head, said Philadelphia Detective Joseph Jenkins, and she believed her patient, who walks with a severe limp.

About 8:30 a.m., police said, the victim's friend saw Johnson sneak into his nurse's bedroom in her first-floor apartment, on Ditman Street near Brill.

She woke up and was shocked to find Johnson on top of her, already in the middle of a sexual act, she told police.

Authorities are charging Johnson with rape and related offenses, Jenkins said.

"There was no sexual relationship between them," Jenkins said.

"He's physically disabled so she just let him come over."

But in a unusual twist, Jenkins said, to fend Johnson off, the victim pulled a 12-inch knife from under her bed and swung it at him and kept him at bay until cops arrived.

"She almost killed him," he said, "but she didn't."

Jenkins said Johnson wasn't injured. *