The next big young-adult novel adaptation landed with a bang (and plenty of enthusiastic screams from the crowd) at Comic-Con International’s Hall H as the folks behind what many consider the next Hunger Games, Sony’s The Mortal Instruments: City of Bones, debuted world-premiere footage and discussed bringing the bestselling series to the screen.

Director Harald Zwart was joined on stage by stars Godfrey Gao, Kevin Zegers, Robert Sheehan, Jamie Campbell Bower and Lily Collins, and the series’ author Cassandra Clare. The group set up the basics of the film – about a young girl named Clary Fray (Collins), whose search for her missing mother uncovers mysteries about her past, and a world that only she can see – before debuting a clip to deafening applause from fans.

Within the footage, Clary confronts Campbell Bower (who plays protagonist – and love interest – Jace Wayland) about why only she can see him. During their discussion, Clary’s mother Jocelyn (played by Game of Thrones’ Lena Headey) is attacked by armed men in her kitchen – she fights back, but eventually submits and drinks a liquid that keeps her from falling prey to the villains. Clary senses something is wrong and rushes home, creeping through the destruction of her home, until a dog attacks her.

The canine eventually transforms into a writhing, tentacle-like creature that looks surprisingly like the monster from The Thing – even with Clary’s attempts to blow it up, its globs of exploded flesh coalesce and once again form the monster. Right before she’s devoured, Wayland swoops in to save her. The crowd seemed pleased with what they’d seen – promising that the adaptation could be true enough to satiate even the most die-hard fans of the novels.

Collins explained she was drawn to Clary because she’s “tenacious and courageous” and “she always finds her own voice within each situation.” She also admitted, “I was a fan of the books before I was cast, and to be a fan cast as a literary heroin that I admired is a dream come true.”

Zwart’s biggest challenge was compressing the book into a “normal movie length.” He explained that he kept what we’ll see on screen as authentic as possible because, “I was working closely with Cassandra on a lot of it, and she was very helpful so it was smooth sailing.”

Clare agreed, saying, “I was pretty interfere-y…there really was almost nothing when I didn't bug Harald about the costumes or sets or story on one level or another. He was sort of introducing me on how to make a movie, and I was talking to him about the stories. It was very collaborative.”

On playing the heartthrob role of Jace, Campbell Bower explained, “I played him as a sassy bitch. What stuck out for me about Jace was this vulnerability that he has…that’s why he sort of puts on this facade of cockiness … he lets his guard down with Clary, and so for him that’s his bag. I made him really grumpy quite a lot of the time, but he needed to be grumpy for you to be able to feel for him later on in the story.”

Zegers – who plays Shadowhunter Alec Lightwood – discussed why the cast attempted not to read ahead, and kept their focus on the first book/film adaptation, despite the wealth of information in all six novels – and he even teased that there could be a second film installment. “You can get ahead of yourself and reveal things that are not meant to be revealed for much later,” he said. “Fortunately, it sounds like we’re going to be able to make at least one more of these. You try to create a character and not look too far ahead and not make any assumptions about him. We try not to get too overwhelmed with the expectation of the entire series and just start it out by making a great story.”

Zwart revealed a fun Easter Egg for fervent fans of the Mortal Instruments series: Clare will have a cameo. “I insisted on having her in the movie,” he explained. “I said, ‘You should be at Magnus Banes’ party where you’re amongst your own creatures! I didn’t cut her out – it was great to have her there!” Of what she’ll be wearing, Clare teased,” I had these metal cat ears that were attached to my head!”

The Mortal Instruments: City of Bones hits theaters on August 21.