Doctor Syn

The Doctor Syn series consists of seven books, set in the eighteenth century. They were all written by Russell Thorndike. By day, the Reverend Christopher Syn is a mild-mannered country vicar. By night, the notorious smuggler known only as the Scarecrow leads his ruthless band across the Romney Marsh, easily defeating the authorities' attempts to capture him. Surely the two can't be connected in any way?

And then there's the question of the notorious pirate, Clegg. Officially, he was caught and hanged shortly after Syn came to the Marsh. But the truth, of course, isn't so straightforward... The events of the series are set from 1754 to c. 1794.

Novels by Russell Thorndike

Doctor Syn: A Tale of the Romney Marsh (1915). Set in either 1794 or 1802. The novel is the chronologically last in the series and features the death of Syn. The finale supposedly features the start of the Napoleonic Wars. But based on the description given, the tale is more likely set at the point Great Britain joined the First Coalition, c. 1794.
Doctor Syn Returns (1935/1936), also known The Scarecrow Rides. There are two versions of the novel, as Thorndike expanded on its events by adding new material. Set in 1775 to 1776. First exploits as the Scarecrow.
Further Adventures of Doctor Syn (1936). Set in 1776 to 1777.
Doctor Syn on the High Seas (1936). Documents the adventures of Syn as Captain Clegg, 1754 to 1775.
Amazing Quest of Doctor Syn (1938). Supposedly set in 1780, though internal details point to c. 1790 instead. Supporting character Dennis Cobtree appears as a toddler in the 1770s, and as a 17-year-old in this novel.
Courageous Exploits of Dr. Syn (1939). Set in 1781.
Shadow of Dr. Syn (1944). Set in 1793.

In 1963 Disney adapted the first novel as a three-part TV Movie called Dr. Syn: The Scarecrow of Romney Marsh; it was later rebroadcast and marketed under the title Dr. Syn, Alias the Scarecrow.

The following tropes are common to many or all entries in the Doctor Syn franchise.
For tropes specific to individual installments, visit their respective work pages.

Badass Preacher: Syn.
Early Installment Weirdness: The first book published ("Doctor Syn") is also the last book in internal chronological order. In various respects, it doesn't quite match the rest of the series; Syn is considerably more brutal and less mentally stable, some characters' ages don't match the ones given in later books, and it's the only book in which Syn's hidden identity is concealed from the reader.
Late Arrival Spoiler: All the books apart from "Doctor Syn" make his triple identity quite clear; so, unless you read in publication order, The Reveal in the first/last book doesn't come as much of a surprise.
The Movie: Captain Clegg and Doctor Syn, both based on the first novel published.
Scarecrow Solution: The Trope Namer
Scary Scarecrows
Spirited Young Lady: Charlotte Cobtree in "Doctor Syn Returns"; her sister Cicely in "The Shadow of Doctor Syn".
Stern Chase: For most of "Doctor Syn on the High Seas", Syn is pursuing his wife and the man who ran off with her. He only catches up with them at the end of "Doctor Syn Returns".
Tontine: In "The Amazing Quest of Doctor Syn".
Truth in Television: Romney Marsh was notorious for smuggling at the time the books are set, and for some decades afterwards. And real-life clergymen were known to be involved with other smuggling gangs.