On Sunday, a miniature Schnauzer named Sissy escaped from her yard in Cedar Rapids, Iowa, walked about 20 blocks to the Mercy Medical Center and sneaked inside to find her human, Nancy Franck, who has been there battling cancer.

ABC News reports security camera footage from the hospital lobby caught the determined dog entering through the automatic doors and wandering around.

Sissy belongs to Nancy Franck, 64, who has been at Mercy Medical Center for about two weeks following cancer surgery. Her husband, Dale Franck, 66, has been caring for Sissy and her brother Barney, also a miniature Schnauzer, at home.

"She was on a mission that night to see her mom," Dale Franck told ABC News, "but she couldn't find the right elevator to take."

Dale Franck noticed Sissy was missing around 1:30 a.m. last Sunday and became frantic. A hospital security officer called him at 5:30 a.m. saying she had found his dog, he said.

"She found my number and house address from her tag on her collar," Dale Franck said. "I was so relieved, and I asked my daughter go and pick her up."

Dale Franck's daughter got permission from hospital staff to take Sissy to Nancy Franck for a quick visit before leaving.

"Nancy and Sissy were able to love each other for a few minutes, and then she went back with me," Dale Franck said. "She's my baby, and though it sounds funny now, it wasn't funny when she was missing. I was worried sick. I'm glad she's OK."

It is a mystery how Sissy found her way 20 blocks to the hospital, but Dale Franck has a theory.

"The only thing I could think of was that Sissy used to ride with me to pick up my wife from work next door to the hospital, but we've never walked that route before," he explained.

Nancy Franck told KWWL it was "a big boost" to visit with her devoted dog.

"It helped a lot," she said, "just to see her and talk to her."

Nancy Franck, who has been battling uterine cancer, is undergoing chemotherapy at the hospital. Doctors say her prognosis is good. Hopefully she and Sissy will be reunited soon.