Season 4 Episodes:
( Production # ) [ Predicted Order Based on Filming ] Airing Order
( 3.19 ) 4.01 - Yanks in the UK: Part One (Sept. 3, 2008)
( 3.20 ) 4.02 - Yanks in the UK: Part Two (Sept. 3, 2008)
( 3.16 ) [ 4.04 ] 4.03 - The Man in the Outhouse (Sept. 10, 2008)
( 3.17 ) [ 4.05 ] 4.04 - The Finger in the Nest (Sept. 17, 2008)
( 4.01 ) [ 4.07 ] 4.05 - The Perfect Pieces In The Purple Pond (Sept. 24, 2008)
( 3.18 ) [ 4.06 ] 4.06 - The Crank in the Shaft (Oct. 1, 2008)
( 3.15 ) [ 4.03 ] 4.07 - The He in the She (Oct. 8, 2008)
( 4.03 ) [ 4.09 ] 4.08 - The Skull in the Sculpture (Nov. 5, 2008)
( 4.04 ) [ 4.10 ] 4.09 - The Con Man in the Meth Lab (Nov. 12, 2008)
( 4.05 ) [ 4.11 ] 4.10 - The Passenger in the Oven (Nov. 19, 2008)
( 4.02 ) [ 4.08 ] 4.11 - The Bone That Blew (Nov. 26, 2008)
( 4.06 ) [ 4.12 ] 4.12 - Double Trouble in the Panhandle (Jan. 22, 2009)
( 4.07 ) [ 4.13 ] 4.13 - Fire in the Ice (Jan. 22, 2009)
( 4.08 ) [ 4.14 ] 4.14 - The Hero in the Hold (Feb. 5, 2009)
( 4.09 ) [ 4.15 ] 4.15 - The Princess and the Pear (Feb. 19, 2009)
( 4.10 ) [ 4.16 ] 4.16 - The Bones That Foam (Mar. 12, 2009)
( 4.11 ) [ 4.17 ] 4.17 - The Salt in the Wound (Mar. 19, 2009)
( 4.12 ) [ 4.18 ] 4.18 - Doctor in the Den (Apr. 2, 2009)
( 4.13 ) [ 4.19 ] 4.19 - Science in the Physicist (Apr. 9, 2009)
( 4.14 ) [ 4.20 ] 4.20 - The Cinderella In The Cardboard (Apr. 15, 2009)
( 4.15 ) [ 4.21 ] 4.21 - Mayhem on the Cross (Apr. 16, 2009)
( 4.16 ) [ 4.22 ] 4.?? - Double Death of the Dearly Departed
( 4.17 ) [ 4.23 ] 4.?? - The Girl in the Mask
( 4.18 ) [ 4.24 ] 4.?? - Beaver in the Otter
( 4.19 ) [ 4.25 ] 4.?? - Critic In The Cabernet