At Project Gutenberg, you can read online or download a plain-text or html version of The Mysteries of Free Masonry, or download a 516 kb PDF version of Morgan's Expose of Free Masonry here. It was over this exposé that William Morgan was said to have been kidnapped and murdered by the Masons. To be honest, I've barely skimmed through it at this point. It seems rather dry. Better to start with a short account of the "excitement" it caused. Scroll down to the third or sixth book below to dip your toe in the waters of one of the hottest cold cases ever. After that, I'm bettin' you'll want more.
Elijah Sedgwick, Jr., a son of my fourth great-grandfather, is named in the Victor Committee on p. 371 of this book, but don't miss the Introduction, which will give you an idea of how highly charged this topic was:
Bernard, David. Light on Masonry: A Collection of All the Most Important Documents on the Subject of Speculative Free Masonry: Embracing the Reports of the Western Committees in Relation to the Abduction of William Morgan...with All the Degrees of the Order Conferred in a Master's Lodge, As Written by Captain William Morgan...By Elder David Bernard. Utica: William Williams, printers, 1829.
Elijah Sedgwick, Jr. (misspelled Sedgewick in this next volume) is named in the dedication on p. iii and again on p. 115 as a member of the Victor Committee:
Southwick, Solomon. A Solemn Warning against Free-Masonry: Addressed to the Young Men of the United States : with an Appendix Containing the Correspondence between Eliphalet Murdock, of Le Roy, Genesee County, N.Y. and the Author, Relating to the Supposed Murder of Mr. Murdock's Father, Through Masonic Vengeance, at Rensselaerville, in the County of Albany, in October, 1803--and Several Other Interesting Matters. Albany: Printed by Geo. Galpin, Office of the National Observer, 1827.
(Incidentally, I notice that another member of the Victor Committee is Samuel Rawson. Elijah Jr. named one of his sons Erastus Rawson Sedgwick (b. 1832). I'm curious to find out what kind of relationship might exist here. Perhaps Rawson was related to Elijah's wife, Esther Bement.)
See p. 109-120 in this volume for an interesting and detailed account of the Morgan story and its political repercussions:
McMaster, John Bach. A History of the People of the United States from the Revolution to the Civil War. New York: D. Appleton and Company, 1908. (Volume V: 1821-1830)
Almost 50 years after the fact, this book was written about the subject:
Bentley, A. P. History of the Abduction of William Morgan, And the Anti-Masonic Excitement of 1826-30, with Many Details and Incidents Never Before Published. Mt. Pleasent, Ia: Van Cise & Throop, 1874.
An anti-Masonic convention was held in 1830:
United States Anti-masonic Convention, Philadelphia, and Myron Holley. The Proceedings of the United States Anti-Masonic Convention, Held at Philadelphia, September 11, 1830. Philadelphia: I.P. Trimble, 1830.
Begin at the bottom of p. 266-270 for another account of the story:
Howe, Daniel Walker. What Hath God Wrought: The Transformation of America, 1815-1848. New York: Oxford University Press, 2007.
The author of this account is a Freemason:
Morris, Stephen Brent. The Complete Idiot's Guide to Freemasonry. New York: Alpha Books, 2006.
This account is also by a Freemason:
Morris, Robert. William Morgan. New York: Robert Macoy, Masonic Publisher, 1883.
Although written in 1899, this article seems as highly charged as any:
Historical Society of Pennsylvania. The Pennsylvania Magazine of History and Biography. [Philadelphia]: Historical Society of Pennsylvania, 1899.
A search for "William Morgan" at Google Books will produce many more volumes on this subject.