What gives Dogs Nightmares?

It is Nudge's responsibility to alert us to any unusual and possibly dangerous goings on in the house. Or so he thinks, and he works hard at this job.
His ideas of danger and ours are not always the same. Rabbits in the yard, a robin on the deck or heaven forbid a cat that doesn't belong to him on the street can send him into a frenzy.
Last night, Peter was working in the spare bedroom - a place where Nudge rarely goes.I heard a low growl and then shrill, "alert! this is serious people - come now" barking.
In all fairness, this paisley cat has a slightly more animated pose than our three, mostly sleepy ones do.