Star Trek: Discovery's Mary Wiseman is opening up about Lorca's (Jason Isaacs) game-changing secret. Sunday's episode revealed that Lorca has been lying about who identity this whole time and is actually from the Mirror Universe. Despite learning about the jaw-dropping twist early on, Wiseman, who plays Cadet Tilly, says the big reveal still took her by surprise.

"When it came out [that Lorca is actually from the Mirror Universe], I was still shocked because Jason [Isaacs] had done a good job — and so had all the writers — of creating a real person in the Prime Universe," she told TV Guide.

Lorca masterfully hid his identity, even passing off his sensitivity to light — a telltale sign that he's not of this universe — as a battle injury rather than a trait seen in all Mirror Universe humans. So when the Discovery crew learns the stunning truth about who he really is, it's going to make them question everything.

Star Trek: Discovery Reveals Lorca's Shocking Secret

"All of our allegiances will be called into question," added Wiseman. "If Lorca is the bad guy [and] we're stuck here in this mirror universe, who do we look to to make the choices that we need to make in order to get out of here?"

New episodes of Star Trek: Discovery stream Sundays at 8:30/7:30c exclusively on CBS All Access.

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Jason Isaacs, Star Trek: DiscoveryJason Isaacs, Star Trek: Discovery