The orange walls of the NCIS squad room kept long-time inhabitants Tony DiNozzo and Timothy McGee so distracted, the agents never realized the skylight creates an acoustic reflection. Their revelation may finally answer how Gibbs always knows what his team is talking about moments before he shows up.

In a sneak peek from tonight's "NCIS," probie agent Bishop (Emily Wickersham) enlightens her teammates that from her desk she can hear all conversations at the foot of the staircase and their colleague Nancy can hear all discussions at Bishop's desk from her cubicle across the room.

This sets off a light bulb for Tony (Michael Weatherly).

"I've been here 15 years and... that's how he does it," the senior NCIS agent proclaims. "Gibbs. That's how he knows everything we're saying. There must be a sweet spot in this room. A little acoustic [makes a pop sound] where he can hear every single thing we say.

"I bet you he comes in here early and he waits and bides his time like a howler monkey in heat, waiting for exactly the right moment to..."

Of course, Gibbs (Mark Harmon) comes in again to finish Tony's thought. Some things will never change.

Tonight's episode explores a little more of Ducky's (David McCallum) backstory and his younger brother who he thought died many years ago, but may still be alive. Check out the two other sneak peeks below.

"NCIS" airs on Tuesdays at 8 p.m. on CBS.