S04E20: Entity
The SGC is invaded by an alien life force that takes up residence in the base computer system -- and in Major Carter.
Previous Episode 
Season 1
Children of the Gods (1)
S1E1 / 27 Jul 1997
Children of the Gods (2)
S1E2 / 27 Jul 1997
The Enemy Within
S1E3 / 01 Aug 1997
Emancipation
S1E4 / 08 Aug 1997
The Broca Divide
S1E5 / 15 Aug 1997
The First Commandment
S1E6 / 22 Aug 1997
Cold Lazarus
S1E7 / 29 Aug 1997
The Nox
S1E8 / 12 Sep 1997
Brief Candle
S1E9 / 19 Sep 1997
Thor's Hammer
S1E10 / 26 Sep 1997
The Torment of Tantalus
S1E11 / 03 Oct 1997
Bloodlines
S1E12 / 10 Oct 1997
Fire and Water
S1E13 / 17 Oct 1997
Hathor
S1E14 / 24 Oct 1997
Singularity
S1E15 / 31 Oct 1997
Cor-Ai
S1E16 / 23 Jan 1998
Enigma
S1E17 / 30 Jan 1998
Solitudes
S1E18 / 06 Feb 1998
Tin Man
S1E19 / 13 Feb 1998
There But For the Grace of God
S1E20 / 20 Feb 1998
Politics (1)
S1E21 / 27 Feb 1998
Within the Serpent's Grasp (2)
S1E22 / 06 Mar 1998
Season 2
The Serpent's Lair (3)
S2E1 / 26 Jun 1998
In the Line of Duty
S2E2 / 03 Jul 1998
Prisoners
S2E3 / 10 Jul 1998
The Gamekeeper
S2E4 / 17 Jul 1998
Need
S2E5 / 24 Jul 1998
Thor's Chariot
S2E6 / 31 Jul 1998
Message in a Bottle
S2E7 / 07 Aug 1998
Family
S2E8 / 14 Aug 1998
Secrets
S2E9 / 21 Aug 1998
Bane
S2E10 / 25 Sep 1998
The Tok'ra (1)
S2E11 / 02 Oct 1998
The Tok'ra (2)
S2E12 / 09 Oct 1998
Spirits
S2E13 / 23 Oct 1998
Touchstone
S2E14 / 30 Oct 1998
The Fifth Race
S2E15 / 22 Jan 1999
A Matter of Time
S2E16 / 29 Jan 1999
Holiday
S2E17 / 05 Feb 1999
Serpent's Song
S2E18 / 12 Feb 1999
One False Step
S2E19 / 19 Feb 1999
Show and Tell
S2E20 / 26 Feb 1999
1969
S2E21 / 05 Mar 1999
Out of Mind (1)
S2E22 / 12 Mar 1999
Season 3
Into the Fire (2)
S3E1 / 25 Jun 1999
Seth
S3E2 / 02 Jul 1999
Fair Game
S3E3 / 09 Jul 1999
Legacy
S3E4 / 16 Jul 1999
Learning Curve
S3E5 / 23 Jul 1999
Point of View
S3E6 / 30 Jul 1999
Deadman Switch
S3E7 / 06 Aug 1999
Demons
S3E8 / 13 Aug 1999
Rules of Engagement
S3E9 / 20 Aug 1999
Forever in a Day
S3E10 / 08 Oct 1999
Past and Present
S3E11 / 15 Oct 1999
Jolinar's Memories (1)
S3E12 / 22 Oct 1999
The Devil You Know (2)
S3E13 / 29 Oct 1999
Foothold
S3E14 / 05 Nov 1999
Pretense
S3E15 / 21 Jan 2000
Urgo
S3E16 / 28 Jan 2000
A Hundred Days
S3E17 / 04 Feb 2000
Shades of Grey
S3E18 / 11 Feb 2000
New Ground
S3E19 / 18 Feb 2000
Maternal Instinct
S3E20 / 25 Feb 2000
Crystal Skull
S3E21 / 03 Mar 2000
Nemesis (1)
S3E22 / 10 Mar 2000
Season 4
Small Victories (2)
S4E1 / 30 Jun 2000
The Other Side
S4E2 / 07 Jul 2000
Upgrades
S4E3 / 14 Jul 2000
Crossroads
S4E4 / 21 Jul 2000
Divide and Conquer
S4E5 / 28 Jul 2000
Window of Opportunity
S4E6 / 04 Aug 2000
Watergate
S4E7 / 11 Aug 2000
The First Ones
S4E8 / 18 Aug 2000
Scorched Earth
S4E9 / 25 Aug 2000
Beneath the Surface
S4E10 / 01 Sep 2000
Point of No Return
S4E11 / 08 Sep 2000
Tangent
S4E12 / 15 Sep 2000
The Curse
S4E13 / 22 Sep 2000
The Serpent's Venom
S4E14 / 29 Sep 2000
Chain Reaction
S4E15 / 05 Jan 2001
2010
S4E16 / 12 Jan 2001
Absolute Power
S4E17 / 19 Jan 2001
The Light
S4E18 / 26 Jan 2001
Prodigy
S4E19 / 02 Feb 2001
Entity
S4E20 / 09 Feb 2001
Double Jeopardy
S4E21 / 16 Feb 2001
Exodus (1)
S4E22 / 23 Feb 2001
Season 5
Enemies (2)
S5E1 / 29 Jun 2001
Threshold (3)
S5E2 / 06 Jul 2001
Ascension
S5E3 / 13 Jul 2001
The Fifth Man
S5E4 / 20 Jul 2001
Red Sky
S5E5 / 27 Jul 2001
Rite of Passage
S5E6 / 03 Aug 2001
Beast of Burden
S5E7 / 10 Aug 2001
The Tomb
S5E8 / 17 Aug 2001
Between Two Fires
S5E9 / 24 Aug 2001
2001
S5E10 / 31 Aug 2001
Desperate Measures
S5E11 / 07 Sep 2001
Wormhole X-Treme!
S5E12 / 08 Sep 2001
Proving Ground
S5E13 / 08 Mar 2002
48 Hours
S5E14 / 15 Mar 2002
Summit (1)
S5E15 / 22 Mar 2002
Last Stand (2)
S5E16 / 29 Mar 2002
Fail Safe
S5E17 / 05 Apr 2002
The Warrior
S5E18 / 12 Apr 2002
Menace
S5E19 / 26 Apr 2002
The Sentinel
S5E20 / 03 May 2002
Meridian
S5E21 / 10 May 2002
Revelations
S5E22 / 17 May 2002
Season 6
Redemption (1)
S6E1 / 07 Jun 2002
Redemption (2)
S6E2 / 14 Jun 2002
Descent
S6E3 / 21 Jun 2002
Frozen
S6E4 / 28 Jun 2002
Nightwalkers
S6E5 / 12 Jul 2002
Abyss
S6E6 / 19 Jul 2002
Shadow Play
S6E7 / 26 Jul 2002
The Other Guys
S6E8 / 02 Aug 2002
Allegiance
S6E9 / 09 Aug 2002
Cure
S6E10 / 16 Aug 2002
Prometheus (1)
S6E11 / 23 Aug 2002
Unnatural Selection (2)
S6E12 / 10 Jan 2003
Sight Unseen
S6E13 / 17 Jan 2003
Smoke & Mirrors
S6E14 / 24 Jan 2003
Paradise Lost
S6E15 / 31 Jan 2003
Metamorphosis
S6E16 / 07 Feb 2003
Disclosure
S6E17 / 14 Feb 2003
Forsaken
S6E18 / 21 Feb 2003
The Changeling
S6E19 / 28 Feb 2003
Memento
S6E20 / 07 Mar 2003
Prophecy
S6E21 / 14 Mar 2003
Full Circle
S6E22 / 21 Mar 2003
Season 7
Fallen (1)
S7E1 / 13 Jun 2003
Homecoming (2)
S7E2 / 13 Jun 2003
Fragile Balance
S7E3 / 20 Jun 2003
Orpheus
S7E4 / 27 Jun 2003
Revisions
S7E5 / 11 Jul 2003
Lifeboat
S7E6 / 18 Jul 2003
Enemy Mine
S7E7 / 25 Jul 2003
Space Race
S7E8 / 01 Aug 2003
Avenger 2.0
S7E9 / 08 Aug 2003
Birthright
S7E10 / 15 Aug 2003
Evolution (1)
S7E11 / 22 Aug 2003
Evolution (2)
S7E12 / 09 Jan 2004
Grace
S7E13 / 16 Jan 2004
Fallout
S7E14 / 23 Jan 2004
Chimera
S7E15 / 30 Jan 2004
Death Knell
S7E16 / 06 Feb 2004
Heroes (1)
S7E17 / 13 Feb 2004
Heroes (2)
S7E18 / 20 Feb 2004
Resurrection
S7E19 / 27 Feb 2004
Inauguration
S7E20 / 05 Mar 2004
Lost City (1)
S7E21 / 12 Mar 2004
Lost City (2)
S7E22 / 19 Mar 2004
Season 8
New Order (1)
S8E1 / 09 Jul 2004
New Order (2)
S8E2 / 09 Jul 2004
Lockdown
S8E3 / 23 Jul 2004
Zero Hour
S8E4 / 30 Jul 2004
Icon
S8E5 / 06 Aug 2004
Avatar
S8E6 / 13 Aug 2004
Affinity
S8E7 / 20 Aug 2004
Covenant
S8E8 / 27 Aug 2004
Sacrifices
S8E9 / 10 Sep 2004
Endgame
S8E10 / 17 Sep 2004
Gemini
S8E11 / 21 Jan 2005
Prometheus Unbound
S8E12 / 28 Jan 2005
It's Good to Be King
S8E13 / 04 Feb 2005
Full Alert
S8E14 / 11 Feb 2005
Citizen Joe
S8E15 / 18 Feb 2005
Reckoning (1)
S8E16 / 25 Feb 2005
Reckoning (2)
S8E17 / 04 Mar 2005
Threads
S8E18 / 11 Mar 2005
Moebius (1)
S8E19 / 18 Mar 2005
Moebius (2)
S8E20 / 25 Mar 2005
Season 9
Avalon (1)
S9E1 / 15 Jul 2005
Avalon (2)
S9E2 / 22 Jul 2005
Origin (3)
S9E3 / 29 Jul 2005
The Ties That Bind
S9E4 / 05 Aug 2005
The Powers That Be
S9E5 / 12 Aug 2005
Beachhead
S9E6 / 19 Aug 2005
Ex Deus Machina
S9E7 / 26 Aug 2005
Babylon
S9E8 / 09 Sep 2005
Prototype
S9E9 / 16 Sep 2005
The Fourth Horseman (1)
S9E10 / 16 Sep 2005
The Fourth Horseman (2)
S9E11 / 06 Jan 2006
Collateral Damage
S9E12 / 13 Jan 2006
Ripple Effect
S9E13 / 20 Jan 2006
Stronghold
S9E14 / 27 Jan 2006
Ethon
S9E15 / 03 Feb 2006
Off the Grid
S9E16 / 10 Feb 2006
The Scourge
S9E17 / 17 Feb 2006
Arthur's Mantle
S9E18 / 24 Feb 2006
Crusade
S9E19 / 03 Mar 2006
Camelot
S9E20 / 10 Mar 2006
Season 10
Flesh and Blood
S10E1 / 14 Jul 2006
Morpheus
S10E2 / 21 Jul 2006
The Pegasus Project
S10E3 / 28 Jul 2006
Insiders
S10E4 / 04 Aug 2006
Uninvited
S10E5 / 11 Aug 2006
200
S10E6 / 18 Aug 2006
Counterstrike
S10E7 / 25 Aug 2006
Memento Mori
S10E8 / 08 Sep 2006
Company of Thieves
S10E9 / 15 Sep 2006
The Quest (1)
S10E10 / 22 Sep 2006
The Quest (2)
S10E11 / 13 Apr 2007
Line in the Sand
S10E12 / 20 Apr 2007
The Road Not Taken
S10E13 / 27 Apr 2007
The Shroud
S10E14 / 04 May 2007
Bounty
S10E15 / 11 May 2007
Bad Guys
S10E16 / 18 May 2007
Talion
S10E17 / 01 Jun 2007
Family Ties
S10E18 / 08 Jun 2007
Dominion
S10E19 / 15 Jun 2007
Unending
S10E20 / 22 Jun 2007
Ben Browder
Cameron Mitchell
Amanda Tapping
Samantha Carter
Christopher Judge
Teal'c
Michael Shanks
Daniel Jackson
Claudia Black
Vala Mal Doran
