The Zygon Who Fell to Earth

The Zygon Who Fell to Earth is an audio drama based on the long-running British science fiction television series "Doctor Who". This audio drama was produced by Big Finish Productions.
Plot.
The Doctor and Lucie are visiting Auntie Pat in the 1980s, where she owns a lakeside hotel and is married to a man named Trevor. Two executives from a record company to convince Trevor, a former folk singer, to make a comeback, but Trevor refuses. That night, Lucie follows the executives to the lake and sees them drinking Skarasen milk before being caught. When Lucie returns to the Doctor she insists that they investigate the cellar, and they find a Zygon body-print machine with the "real" Trevor inside.
The Doctor and Lucie reveal to Pat that her husband is a Zygon, but she already knows, and loves him anyway. Lucie returns to the executives, and it is revealed that they are all Zygons in disguise. They need to recover a vital control crystal from Warmaster Hagoth – Trevor – but he has given it to Pat as a brooch, and now it's fused to the skin of her throat. When the executives kidnap Pat, the Doctor and Trevor follow her to the Zygon ship, with the fake Lucie in tow. On the ship, the Doctor rescues the real Lucie and outs the fake.
The Zygons rip the brooch from Pat's throat, killing her in the process and allowing them to arm warheads and launch an attack on the Earth. Trevor, distraught over Pat's death and not caring about his own life, allows the Doctor and Lucie to escape and then commands the Skarasen to attack and destroy the ship, stopping the Zygon plot. Lucie is unable to accept that her Auntie Pat is dead, since she knew her in the future. Once Lucie has gone to sleep Trevor returns in his Zygon form. Using the last of his strength he permanently takes the form of Auntie Pat and resolves to live an ordinary life and allow Lucie to believe the real Pat survived.
Radio broadcast.
Following its release on CD, "The Zygon Who Fell to Earth" was broadcast in the UK on BBC Radio 7 on 23 November 2008, the 45th anniversary of "Doctor Who".