Doctor Who Day is celebrated in every corner of the globe on November 23 because the first episode of the popular BBC science fiction series was aired on that date in 1963. Actors like Christopher Eccleston, David Tennant, Matt Smith, Peter Capaldi and Jodie Smith have since then played the timelord, who regenerates every few seasons and tries to keep the universe in order.

With David Tennant reappearing as the 14th incarnation of the Doctor and Sex Education star Ncuti Gatwa as the 15th doctor, the upcoming seasons of Dr Who promise more excitement and cosmic scare. Here we take a look at the top five scariest episodes from the series.

Blink (2007) – Season 3, Episode 10

Written by Steven Moffat, Blink is one of the most memorable episodes of Doctor Who not just because of the terrifying plot, but also because it introduces one of the most deadly villains of the show. The entire episode relies on Sally Sparrow (Carey Mulligan) and her boyfriend Larry Nightingale (Finlay Robertson).

Sally receives a cryptic message left on 17 DVDs by David Tennant’s Doctor, who warns her, “Don’t Blink. Blink and you’re dead.” The couple realise that they are battling an alien power in the form of ‘Weeping Angels’, while the Doctor instructs them solely via a pre-recorded video. The brilliance of the episode lies in the fact that Sally doesn’t even meet the Doctor until 2008, while the episode takes place in 2007.

Silence in the Library and Forest of the Dead (2008) – Season 4, Episode 8 & 9

“Hey! Who turned out the lights?” — imagine this line being spoken by a spacesuit-clad skeleton in a library. That is the premise of the two-part episode Silence in the Library and Forest of the Dead.

The Doctor (Tennant) brings Donna (Catherine Tate) to a planet-sized library only to discover that it is devoid of life. While the time-travelling partners start discovering mysteries of the library, an archaeologist River Song (Alex Kingston) arrives with her team to the 51st century library. The group soon discovers that the library is filled with a sinister force that could take the form of someone’s own shadow slowly eating away to leave a skeleton in the place of a living human.

Midnight (2008) – Season 4, Episode 10

Though Blink is widely regarded as the scariest episode of Dr Who, Midnight is easily one the most terrifying and unsettling episodes of the show. This is the first time that the nature of the enemy is not revealed in the science fiction series.

The Doctor (Tennant) and Donna take a vacation to spend time on a planet called Midnight. While Donna enjoys her time at the spa, the Doctor goes on a bus tour to the Sapphire Waterfall. The four-hour journey takes a halt when the bus stops for no reason and a passenger gets taken over by an entity that repeats anything anyone says. Slow at first, the entity soon becomes adept enough to go from mimicking the Doctor to talking before he can speak. The most spine chilling moments of the episode is where the Doctor realises that the entity is taking over his mind while the passengers turn against him.

Water of Mars (2009) – Special Episode

Set in the year 2059, the Tenth Doctor (Tennant) struggles to face his prophesied death while travelling to Mars to witness the historic moment when humans first colonise Mars. Written by Russel T. Davies, Water of Mars won the 2010 Hugo Award for Best Dramatic Presentation, Short Form.

The Doctor meets Adelaide Brooke (Lindsay Duncna), captain of the mission who is struggling to keep things afloat in a mission gone wrong. The Doctor soon comes face to face with the reason behind the failing mission in the form of a water-bound alien force that wants to take over Earth. The Doctor not only has to face a deadly villain, but also has to choose whether he wants to change the death of the crew members that are already set in time.

Night Terrors (2011) – Season 6, Episode 9

While David Tennant’s 10th Doctor took the most amount of hits when it came to scary episodes, Night Terrors, starring Matt Smith as the 11th Doctor, is bound to make you relive your childhood nightmares. Pop culture has often seen dolls becoming the subject of horror, but the life-sized dolls in the 2011 episode makes a child’s nightmare come true.

The age-old story of a young boy afraid of monsters in his bedroom takes a turn when the Doctor, Amy (Karen Gillian) and Rory (Arthur Darvill) realise that the child’s cupboard is filled with a race of giant dolls that transform people into the same. Filled with jump scares and terrifying visuals, the episode will make you throw away all the dolls in your house.