Symbolism, Imagery, Allegory
He'd looked out the window where fields of white poppies stretched all the way to the shadowy hills. The whiteness hurt his eyes, and so he turned from them with relief to the cool darkness inside.
[...]
The poppy fields weren't completely deserted. Now and then he saw horses – he knew them from picture books – walking between the rows of white flowers. (2.11-12)
Our first glimpse of Opium and what do we get? Flowers. Sounds pretty enough. But these flowers are also sinister, even scary. This is the only view from Matt's window, and though at first glance it seems beautiful, it ends up hurting his eyes. They're beautiful, but dangerous. He's forced to retreat back into his cozy home with Celia.
The flowers aren't the only things that are appealing at first, only to later become menacing. El Patrón, too, at first meeting, seems like the kind of guy we'd all want to hang around. But he's dark, dangerous, and deadly. Remember, appearances in Opium can be quite deceiving.