Sometimes things lurk below the surface which only the Doctor can see. From a moon with poison seas, to a 19th-century health spa, even somewhere as everyday as a furniture store on a Sunday afternoon - there are always hidden depths and unseen dangers to uncover! 3.1 The Seas of Titan by Lizbeth Myles Out on Saturn's moon, Titan, an outpost all-but-forgotten by Earth struggles on against the odds. As the Doctor joins explorers deep in the methane seas, they discover a hidden civilisation. But will the Sea Devils prove to be the colony’s salvation or its final destruction? 3.2 Lay Down Your Arms by Lisa McMullin

1864. Instead of relaxing at the Bad Homburg Spa, its visitors are fighting. And Bertha Kinzky, housekeeper to Alfred Nobel, is appalled. Perhaps the mysterious Herr Schmidt can help? Soon, Bertha is contending with aliens, as well as her mother’s matchmaking, as she and the Doctor try to keep the peace. 3.3 Flatpack by John Dorney Liv Chenka and Tania Bell are spending Sunday afternoon on that most traditional of couple activities. Furniture-shopping! But just how long has London's newest Flatpack store been open? Who is its mysterious manager? And is it even Sunday? Liv is about to run into a very old friend.