Inferno is a 2013 mystery thriller novel by American author Dan Brown and the fourth book in his Robert Langdon series, following Angels & Demons, The Da Vinci Code and The Lost Symbol.

Harvard symbolism professor Robert Langdon wakes up in a hospital in Florence, Italy, with a head wound and no memory of the last few days.

Dr. Sienna Brooks, one of the doctors tending to him, reveals that he is suffering from amnesia and hearing a woman's voice repeatedly saying "seek and find".

Langdon opens the container and finds a small medieval bone cylinder fitted with a hi-tech projector (Faraday Pointer) that displays a modified version of Botticelli's Map of Hell, which is based on Dante's Inferno.

At the Palazzo, Langdon meets a guide of the museum, Marta Alvarez, who recognizes him, having met him and Ignazio Busoni, the director of Il Duomo, the previous night, when she showed them Dante's death mask.

Langdon connects the phrase "Paradise 25" to the Florence Baptistry, where they find the Dante mask containing a hidden riddle from its current owner, a billionaire geneticist named Bertrand Zobrist.

He also left a video filled with disturbing Dante imagery, and then showed a picture of the plague container kept in a hidden underwater location.

The plague that Zobrist created is revealed to be a vector virus that randomly activates to employ DNA modification to cause sterility in one third of humans.

[4] The cover depicts the famous Basilica di Santa Maria del Fiore located in Florence, Italy.

The ebook was distributed for free to readers worldwide through online e-book stores like Amazon, Google Play and Barnes & Noble until March 24, 2013.

Inferno has been translated into French, Russian, Turkish, Greek, German, Dutch, Spanish, Catalan, Italian, Czech, Portuguese, Finnish, Norwegian, Swedish and Danish for simultaneous release.

The New York Times praised the book as being "jampacked with tricks" and said that Langdon is on "one of those book-length scavenger hunts that Mr. Brown creates so energetically.

"[14] The Boston Globe's Chuck Leddy compared the book favorably to Brown's previous works, and deemed it "the kind of satisfying escapist read that summers were made for.

"[16] Samra Amir of The Express Tribune was critical of the novel's predictability and malapropism, but noted that "Brown's art reigns over boredom.

"[17] Writing for The Guardian, Peter Conrad dismissed the book's content as "conspiratorial farrago" and further elaborated: "Inferno is also dreadful, abounding in malapropisms and solecisms, leaden restatements of the obvious and naive disinformation about the reality outside the bat-thronged belfry that is Brown's head.

"[18] The novel received backlash from Filipinos[19] after a character named Sienna Brooks, narrating through flashbacks, recounts being sexually assaulted in a Manila slum after volunteering in a humanitarian mission in the Philippines.

Despite slipping 42% in its second week, Inferno far outpaced the #2 book, Khaled Hosseini's And the Mountains Echoed, which posted a debut of 91,000 copies.