As a mystery, The Black Tower is full of plot holes, a disappointment after the first book dramatized in Acorn TV’s Dalgliesh series, Shroud for a Nightingale, which was tightly and deftly plotted. The Black Tower, however, is troubling. The big reveal is a surprise — the genre demands it, after all — but it seems outlandish and hurried. However, The Black Tower compensates with star turns by Stephen Mackintosh and Mirren Mack (who was so outstanding in Acorn TV's The Nest), a fearless dive deep into Adam Dalgliesh’s soul, and an examination of how people with disabilities, advanced age, or illness can be marginalized and underestimated.
My body is my prison and I would be so obedient to the Lord as not to break prison. I will not hasten my death starving or macerating this body.
A panoramic shot that swoops over a rural landscape speckled with gorse, above an imposing Georgian house and an ancient stone structure (The Black Tower of the title) and to the cliffs and sea beyond. The idyllic landscape is broken by a man in a wheelchair being pushed by a figure in a monk’s habit, and they are quarreling violently. At the cliff’s edge, Victor (Darren Swift), alone in his wheelchair, gazes at the sky, the birds, and the sea, before the wheels rapidly turn, and he falls to his death.
Dalgliesh has come to visit an old family friend, Father Michael, who is a spiritual advisor to the inhabitants of Toynton Grange, a small nursing home. Michael had written to Dalgliesh asking for advice. Looking around the interior of Michael’s cottage, Dalgliesh finds a funeral notice: Michael died two weeks ago. This is another loss his life, following on from that of his wife and, as we learn in this episode, a child.
Maggie (Mack), arrives at the cottage. She’s married to the doctor on staff. There are only four residents; ever since Victor’s death, they’ve had trouble filling beds. Michael died of a heart attack after hearing a confession from one of the patients and was found in his armchair wearing his clerical robe and stole. Dalgliesh pokes around Michael’s desk, where he finds poison-pen letters. He visits the Grange and meets creepy Wilfred Austey (Mackintosh), owner and director of the nursing facility; given to grand gestures, manipulation, and a love of ritual. He rules the facility as though it is his kingdom, turning on the charm when required.
Dalgliesh is visited later that evening by Helen (Sally Scott), the facility’s nurse, who comes bearing clean linens and that their patient Grace was the last to see Michael, who had not been well, his death came as no surprise. The night of his death, someone was supposed to visit him to make sure all was well, but because of a scheduling mishap, Michael died alone. Dalgliesh visits Grace (Jenny Howe), whose task is to gather eggs from the hens. Wilfred likes to keep everyone busy, apparently. She’s lived there for four years and likes being close to the sea, although she poignantly mentions she’s never seen it.
Dalgliesh returns a book of poetry by Thomas Hardy, which Michael had borrowed, and they chat about Dalgliesh’s own writing. But she tells him one significant fact: Michael, following her confession, removed his stole and left it. Grace's other job, running the mailing list of Graystone’s supporters (it's the 1970s when you had to type up mailing labels. On a typewriter). She has the list memorized, likes to imagine people’s appearances from their names, and takes pride and pleasure in her work. But she confesses to Dalgliesh that she, too, received a poison-pen letter and recognizes the individual marks that identify it as a product of her typewriter.
Julius (Jonjo O’Neill), an old school friend of Wilfred’s, a former diplomat, has villain written all over him. He introduces Adam to patient Henry (George Robinson), who has made a very lifelike clay model of Wilfred’s head and shy, awkward handyman Dennis. Julius also tells Dalgliesh the story of how Wilfred, sick and apparently incurable by modern medicine, went on a pilgrimage to Lourdes and returned fit and healthy. It was then he decided to convert his family home to a nursing facility, and twice every year, a group pilgrimage is made to Lourdes, using the new minibus Julius bought. Wilfred is very enthusiastic about visits to Lourdes.
Dalgliesh is invited to lunch, and meets Maggie’s husband, medical officer Eric Newson (John Hollingworth), and patients Jennie (Storme Toolis) and Ursula (Shannon Murray). He then explores the grounds, where Wilfred explains that the door is always kept open since his great-grandfather restored the tower and, awaiting the Revelation, walled himself up alive. Wilfred now uses the tower for meditation. Simon, to whom Victor was particularly unpleasant, claims Victor told him to leave, and he retreated too far away to save him.
As Dalgliesh heads to the local police, Maggie flings herself into the car and demands a lift into town; hanging out of the car window like an eager Labrador, tells Dalgliesh that she liked Victor and enjoyed his savage wit. In town, DI Daniel (Barry Aird) assures Dalgliesh it was suicide and has Kate Miskin (Carlyss Peer) show him out. But Kate disagrees with her boss and will dig around for Dalgliesh. Back at the facility, the Black Tower is on fire. Dalgliesh and Daniel run to the building and find the door locked, break it down, and discover Wilfred inside.
Julius holds a dinner party, where Maggie invites Dalgliesh to dance and breaks a glass, effectively ending the party. Adam takes a drunken Henry home, who confesses he was in love with a patient Peter, who Wilfred sent away. Victor found out Peter died. Henry also has a poison-pen letter, as does Eric; he had an affair with Maggie — covered up by Wilfred, who forced them to marry. Maggie still loves Eric, whereas he regards her as an embarrassing liability. And then Grace is murdered. Dalgliesh uses his seniority to get the post-mortem, but the sulky pathologist claims the question should be why she was still alive.
Wilfred announces Grace’s death and says he's decided to hand over the facility to the Ridgewell Trus, but he wants the decision to be made as a family. But the vote isn't about the transition; it's to decide if Wilfred should continue as their spiritual advisor. Dennis gives an emphatic yes; Jenny and Ursula agree; Henry votes against it. Eric has to agree. Maggie doesn’t have a vote and she’s furious, but Eric refuses to stand up for her; and when she bursts in on Eric and Helen, displaying a very unprofessional level of intimacy, she's had enough. She starts packing, planning an escape.
Dalgliesh returns to find Maggie dead, hanging in the tower. Julius is shocked and upset; she’d arrived distraught, but he’d calmed her down and he felt safe leaving her there to attend Wilfred's meeting. Kate unpacks Maggie’s suitcase and she and Dalgliesh are surprised to find Maggie’s best clothes inside, along with his pen. It’s not the act of a woman planning suicide. But Dalgliesh, so intent on justice originally, mentions that he’s tired of the case. The seascape has raised memories of his dead wife; he dreams she beckons him to join her.
Before their departure, Wilfred and Helen flap around, distressed that the mailing list of supporters seems to have disappeared. Dalgliesh interviews everyone to work out a timeline for the afternoon. The patients present a bleak picture of their life at the Grange; Jennie comments that Eric should burn in hell, and Adam recognizes a favorite phrase of the poison-pen letters. He’s furious and demands she apologize to the surviving victims. Yet Ursula, Jennie, and Henry tentatively ally. They consider themselves the originals, the survivors, who should stick together. Wilfred is no part of their family.
Dalgliesh confronts Wilfred with the recent discovery that the story of his Lourdes cure was a lie, and Victor knew. Wilfred laughs, loads his charges into the van, and they drive off. At the police station, Kate receives an important message from the Foreign Office about Julius’s background. She calls Toynton Grange and is suspicious when Julius answers and tells her Dalgliesh has left. He hasn’t. Instead, he’s put together Toynton Grange is a front for a drug smuggling operation masterminded by Julius, who has time and money on his hands.
Julius pulls a gun on Dalgliesh and talks. The drugs are hidden in the wheelchairs; who would ever suspect a minibus full of people with disabilities? Julius persuaded Dennis Victor knew, murdered Michael and Grace’s death was Dalgliesh’s fault because he wouldn’t let things alone. And Julius had to kill Maggie because she’d figured it out too. He forces Dalgliesh at gunpoint to drive them to the cliffs. When Kate arrives at the house, she finds Dalgliesh’s pen, which he’d deliberately dropped on the ground, and calls for reinforcements. Julius, knowing he will be arrested, tips himself over the edge of the cliff. The camera performs the opening shot of the two-parter in reverse, away from the sea and over the tower and the house.