A few hours ago Ddog ran inside from the garden, she growled towards the garden as if she was frightened. No one in the garden as far as I can tell but I did lock the door to be on the safe side. She's been quite whiney since and has mostly been sat on the stairs looking out towards the garden (rather than her usual spot on the sofa). She attempted to go out but peeked her head out and ran back in. I can't see, hear or smell anything out there (although I know they have much better smell and heating than us so perhaps something like that). Our neighbours gardens are directly next to ours with just a regular fence dividing to she's used to hearing different voices/people doing diy/children/cars etc from the garden. I was going to go outside with her to show her it's okay but she ran and hid upstairs? What could have got her so scared?