Home Security (Please pardon post length. I'm wired.) [View all]
"Wait, what was that?"

Dog (Shadow) hears someone(thing) approaching front door.
Instinctively knowing mommy/daddy asleep
dog goes on alert barks once, wakes up cat KC,
barks again, waking humans, barks twice, startling cat and
turning on instant porch flood light in low wall-mounted nitelite,
while anxious dog trots down hallway tentatively followed by
also anxious cat as intruder attempts uninvited entry through
unlocked front door and dog viciously yarks and barks rapid fire
as screen door tries to open but cannot due to seventy-pound dog pushing against it while aroused and pissed-off cat leaps repeatedly
at inner door scratching madly at custom-made claw-proof chalkboard-like surface producing terrible, terrifying, maximally annoying noise like fingernails deliberately drawn down forcibly on an actual chalkboard all of which results (documented tests have proven) in emotional response* from frustrated pseudo-intruder, which triggers tendencies from the fight or flight gene, acting as the body's primary self-defense mechanism. Bottom line pets prevent fleeing felon from disturbing their peace.
Both animals receive extra nighty-nighty treats. And suggest
strongly that mommy/daddy lock their damn door from then
on.
*With apologies to Wikipedia for emotional response reference