Greta pressed her body against her owner, remaining still for a moment before suddenly going alert.

The dog growled—a sound that wasn’t fearful, but rather protective. The woman, puzzled, tried to sit up, but then she saw Greta leap between her and the doctors who were preparing to take her for surgery.

“Greta, what are you doing? Quiet!” she cried, alarmed. But Greta continued to growl.