Cliffhanger

A cliffhanger is a standard device of serial fiction. It involves the heightening of dramatic tension at the end of an episode to such a degree that the viewer is made anxious about the fates of the protagonists. This, the producers of the work hope, will inspire viewers to return for the next episode, so that they can see how — or if — the protagonists survived.

Cliffhangers were included at the end of almost every episode of the 1963 version of Doctor Who. Most typically, the only episode free of cliffhangers was the last one in a serial, although there were periods — such as most of the 1960s and season 19 — where even these episodes had at least mild cliffhangers.

The device is still used in the BBC Wales version of the show for multi-episode storylines. A cliffhanger has also been a nearly-universal feature of the the last episode of a series, in which it serves to point to that year's Christmas special.

Cliffhangers are less prominent parts of Torchwood narratives, although each episode of Children of Earth used them. Conversely, The Sarah Jane Adventures regularly employs cliffhangers, in a style that directly echoes so-called "classic" Doctor Who. SJA stories universally have cliffhangers between parts one and two. Series-ending cliffhangers are much less common in the spin-off series. Only the Torchwood series 1 finale ends in a cliffhanger that is directly resolved in a later episode. Unusually, this cliffhanger resolves in both DW: Utopia, and TW: Kiss Kiss, Bang Bang, and it is not strictly necessary to have seen Utopia to understand its Torchwood resolution.

Season One - 1963-64

 * An Unearthly Child Episode 1 - The Doctor kidnaps Ian and Barbara and The TARDIS is sent to 100,000 BC.
 * The Cave of Skulls Episode 2 - The Doctor and his companions are chased into the Forest of Fear by Za and Hur.
 * The Forest of Fear Episode 3 - Kal and his tribal warriors stops The Doctor and his companions reaching the Tardis.
 * The Firemaker Episode 4 - The Tardis detects readings of Dangerous Radiation.
 * The Daleks Episode 1 - Barbara is cornered by a Dalek.
 * The Survivors Episode 2 - Susan collects the Anti-Radiation drugs in the Tardis and prepares to go back to the city.
 * The Escape Episode 3 - The Doctor,Susan,Barbara and Ian (Disguised as a Dalek) try to escape the Dalek City.
 * The Ambush Episode 4 - Ian leaves an empty fluid link in the Dalek City and it must be retrieved.
 * The Expedition Episode 5 - Elyon is killed by creature in the Lake of Mutations
 * The Ordeal Episode 6 - Antodus falls down a abyss and Ian (who is holding his rope) is dragged towards the edge.
 * The Rescue Episode 7 - The Tardis Console explodes and the Tardis crew fall to the floor.
 * The Edge of Destruction Episode 1 - As The Doctor works on the Console he is grabbed by the throat.
 * The Brink of Disaster Episode 2 - The Tardis materializes on a cold,snowy area with a giant footprint on the ground.
 * The Roof of the World Episode 1 - Lord Tegana buys a poison to use on the Caravan's water supply.
 * The Singing Sands Episode 2 - Tegana is sent to find desperately needed water, finds an Oasis but doesn't send any water back.
 * Five-Hundred Eyes Episode 3 - The Doctor,Susan and Ping-Cho go to a cave where they find that a painting of eyes are moving.
 * The Wall of Eyes Episode 4 - Ian tries to escape the Caravan and finds a dead guard.
 * Rider from Shang-Tu Episode 5 - Tegana holds Susan hostage.
 * Mighty Kublai Khan Episode 6 - Tegana threatens Ping-Cho
 * Assassin at Peking Episode 7 - None.
 * The Sea of Death Episode 1 - Arbitan is killed by a Voord.
 * The Velvet Web Episode 2 - The Doctor's allies try to find the second key of Marinus.
 * The Screaming Jungle Episode 3 - None.
 * The Snows of Terror Episode 4 - Vasor is killed by the Ice Soldiers
 * Sentence of Death Episode 5 - Susan is kidnapped and The Doctor is threatened to stop investigating the murders.
 * The Keys of Marinus Episode 6 - None.
 * The Aztecs Episode 1 -
 * The Aztecs Episode 2 -
 * The Aztecs Episode 3 -
 * The Aztecs Episode 4 -
 * The Sensorites Episode 1 -
 * The Sensorites Episode 2 -
 * The Sensorites Episode 3 -
 * The Sensorites Episode 4 -
 * The Sensorites Episode 5 -
 * The Sensorites Episode 6 -
 * The Reign of Terror Episode 1 -
 * The Reign of Terror Episode 2 -
 * The Reign of Terror Episode 3 -
 * The Reign of Terror Episode 4 -
 * The Reign of Terror Episode 5 -
 * The Reign of Terror Episode 6 -

Season Two - 1964-65

 * Planet of Giants Episode 1 - The Doctor,Barbara and Susan (Micro-Sized) are attacked by a Cat.
 * Dangerous Journey Episode 2 - The Doctor and Susan nearly drown in a drainpipe.
 * Crisis Episode 3 - None.
 * World's End Episode 1 - The Doctor and Ian are surrounded by Robomen and are shocked to see a Dalek rising out of the River Thames.
 * The Daleks Episode 2 - The Resistance prepares to fight the Daleks.
 * Day of Reckoning Episode 3 - A firebomb is placed near the Doctor,Susan and David Campbell's hideout.
 * The End of Tomorrow Episode 4 - The Slyther attacks Ian and Larry Madison.
 * The Waking Ally Episode 5 - Ian's hiding place is prepared to be dropped down a mine shaft.
 * Flashpoint Episode 6 - None.
 * The Rescue Episode 1 -
 * The Rescue Episode 2 -
 * The Slave Traders Episode 1 - Ascaris prepares to Assassinate the Doctor.
 * All Roads Lead to Rome Episode 2 - Ian and Delos are forced to fight Lions.
 * Conspiracy Episode 3 - Nero forces Ian and Delos to fight each other to the death.
 * Inferno Episode 4 - The Tardis is sent off course.
 * The Web Planet Episode 1 - The Doctor finds the Tardis is missing.
 * The Zarbi Episode 2 - The Doctor confronts Animus.
 * Escape to Danger Episode 3 - Ian and Vrestin fall into a tunnel.
 * Crater of Needles Episode 4 - Barbara is attacked by the Zarbi.
 * Invasion Episode 5 - None.
 * The Centre Episode 6 - None.
 * The Crusade Episode 1 -
 * The Crusade Episode 2 -
 * The Crusade Episode 3 -
 * The Crusade Episode 4 - The Tardis loses power.
 * The Space Museum Episode 1 -
 * The Dimensions of Time Episode 2 -
 * The Search Episode 3 -
 * The Final Phase Episode 4 -
 * The Executioners Episode 1 - The Doctor and Barbara find a Dalek in the Aridian desert.
 * The Death of Time Episode 2 - The Supreme Dalek vows to seek revenge on the Doctor.
 * Flight Through Eternity Episode 3 - None.
 * Journey into Terror Episode 4 - The Daleks create an Android double of the Doctor with orders to 'Infiltrate and Kill'.
 * The Death of Dr Who Episode 5 - The Doctor and his companions are met by a Mechanoid.
 * The Planet of Decision Episode 6 - None.
 * The Watcher Episode 1 - The Monk imprisons the Doctor.
 * The Meddling Monk Episode 2 - None.
 * A Battle of Wits Episode 3 - Steven and Vicki find the Monk has a Tardis and is the same species as the Doctor.
 * Checkmate Episode 4 - None.

Season Three - 1965-66

 * Four Hundred Dawns Episode 1 - The Doctor discovers the planet he is on will be destroyed in two days.
 * Trap of Steel Episode 2 - None.
 * Air Lock Episode 3 - None.
 * The Exploding Planet Episode 4 - The Doctor and his companions travel to Kembel and find Jeff Garvey.
 * Mission to the Unknown - Marc Cory is exterminated by the Daleks and they form an alliance to conquer the Sol system.
 * The Myth Makers Episode 1 -
 * The Myth Makers Episode 2 -
 * The Myth Makers Episode 3 -
 * The Myth Makers Episode 4 -
 * The Nightmare Begins Episode 1 - The Doctor and his Tardis are surrounded by Daleks.
 * Day of Armageddon Episode 2 - Bret Vyon tries to leave in his ship and abandon the Doctor.
 * Devil's Planet Episode 3 - Katarina finds Kirksen.
 * The Traitors Episode 4 - Sara Kingdom orders Borkar to find The Doctor and Steven.
 * Counter Plot Episode 5 - The Daleks defeat the Invisible Creatures and the Doctor faces the fact that "the Daleks have won."
 * Coronas of the Sun Episode 6 - The Tardis arrives on Kembel (which now has a poisonous atmosphere).
 * The Feast of Steven Episode 7 - None.
 * Volcano Episode 8 - The Daleks chant for victory.
 * Golden Death Episode 9 - Sara and Steven are attacked by a Roman soldier and a Mummy awakens.
 * Escape Switch Episode 10 - The Tardis Console flashes and the Directional Control burns out.
 * The Abandoned Planet Episode 11 - Mavic Chen hold the Doctor and his companions prisoner.
 * The Destruction of Time Episode 12 - None.
 * War of God Episode 1 - The Abbot of Amboise is revealed to be the Doctor's exact double.
 * The Sea Beggar Episode 2 - None.
 * Priest of Death Episode 3 - Steven is framed for murder and is chased by a mob.
 * Bell of Doom Episode 4 - None.
 * The Ark Episode 1 -
 * The Ark Episode 2 -
 * The Ark Episode 3 -
 * The Ark Episode 4 - The Doctor mysteriously vanishes from the Console Room.
 * The Celestial Toymaker Episode 1 -
 * The Celestial Toymaker Episode 2 -
 * The Celestial Toymaker Episode 3 -
 * The Celestial Toymaker Episode 4 -
 * The Gunfighters Episode 1 -
 * The Gunfighters Episode 2 -
 * The Gunfighters Episode 3 -
 * The Gunfighters Episode 4 -
 * The Savages Episode 1 -
 * The Savages Episode 2 -
 * The Savages Episode 3 -
 * The Savages Episode 4 -
 * The War Machines Episode 1 - The hypnotised Dodo is ordered to bring the Doctor to be hypnotised by WOTAN.
 * The War Machines Episode 2 - Ben is cornered by a War Machine
 * The War Machines Episode 3 - The Doctor confronts a War Machine.
 * The War Machines Episode 4 - None.

Season Four - 1966

 * The Smugglers Episode 1 -
 * The Smugglers Episode 2 -
 * The Smugglers Episode 3 -
 * The Smugglers Episode 4 -
 * The Tenth Planet Episode 1 - A group of soldiers sent to investigate the Tardis are killed by Cybermen.
 * The Tenth Planet Episode 2 - The Radar Technician in Snowcap detects a Cyber-Fleet heading for Earth.
 * The Tenth Planet Episode 3 - The Countdown for the Z-Bomb launch reaches Zero.
 * The Tenth Planet Episode 4 - The Doctor Regenerates into a new form.

As documentary subject
The quality of various cliffhangers — in terms of their efficacy to make viewers return the next week —was the subject of a short documentary on BBC DVD.