Intellectual scrutiny gives way to indulgent ego trips in “Bloodline,” a documentary by Bruce Burgess, a third-rate conspiracy theorist who makes Morgan Spurlock look Pulitzer-worthy.

Given the film’s admirable intentions, it’s a shame how quickly things derail for the wide-eyed believer. Having read Dan Brown’s revisionist best-seller “The Da Vinci Code,” and a handful of other books about religious secrecy and conspiracies, Mr. Burgess commits himself to investigating the groundbreaking claims about Jesus Christ and Mary Magdalene made by Mr. Brown’s popular book (among other sources). There’s nothing wrong with bringing some critical perspective to a popular fad. As for the perspective, well …

Early on, we find Mr. Burgess at the library (camera crew in tow), poring over old microfilm. But it isn’t long before we’re following along on his quest to track down sources who will attest to the fact that Jesus Christ did not die on the cross, nor rise from the dead, but instead married Mary and fathered her children.

As his early search for evidence bears little fruit and the film’s intriguing clues begin to give way to a mushy form of theory and speculation, “Bloodline” becomes less about truth than about the dangers of getting too close to the truth. Or so the filmmaker would have us believe. At a diner, Mr. Burgess is handed a cryptic warning by a stranger. The camera is turned off, of course. When he finally meets with an amateur archaeologist, the man expresses fears about his safety. A simple B-roll shot of Mr. Burgess crossing a London street is given an ominous musical background.

The unshaven filmmaker keeps himself in on the action, looking nervously into the camera during a series of late-night confessions in which he says that he feels as though he is getting too close to something, and that danger is near. During one such monologue, Mr. Burgess expresses anger at critics who might doubt his fears and assertions. Yes, Mr. Burgess says, there are those who will condemn his lack of scientific evidence or sound practices, but he just knows it to be true: Jesus was a father, and the Catholic Church is built on a lie.

Perhaps if Mr. Burgess had unearthed anything of the empirical sort, his movie would be opening on more than just New York screens. Maybe if his most recent television projects didn’t sport titles such as “Bigfootville” and “The Bermuda Triangle Solved?” we’d be more inclined to consider his assertions.

“Bloodline” starts, in many ways, where “The Da Vinci Code” did, namely with discussions of famous artworks that supposedly contain hidden clues about how the church has deceived its followers through the centuries. Various cryptic interviews with thirdhand sources and obvious hucksters ensue. One ragtag archaeologist who has unearthed a handful of glass bottles with suspiciously pristine maps and notes inside — his lack of gloves or tweezers ensures that they won’t be pristine for long — lives in a mobile trailer park.

“The Da Vinci Code” phenomenon was premised, to a large degree, on the populist idea that anyone can dig for history and thereby alter it. Late in “Bloodline,” Mr. Burgess confirms the point, ranting that his trailer-park friend is just as qualified to make a world-changing discovery as anyone, and that archaeology is as much for guys who break open bottles as for Ph.D.s.

Those who value evidence, scientific technique, and objective documentary filmmaking might add that a little common sense always helps.