It looks like Castle (Nathan Fillion) is returning to work as a private investigator in the upcoming eighth season of ABC's Castle.

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A new promo for Castle season 8 has been released, centered around Castle being a P.I. The narration even says, "This fall, a mystery writer becomes a full-time private investigator. What could possibly go wrong?"

The actual footage shown is from season 7, when Castle got into work as a P.I. after being fired by the NYPD. However, this promo allegedly aired on ABC this week.

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It is currently unknown how or why Castle would get into work as a private investigator again, though the dynamic of the show is changing. Beckett (Stana Katic) has been promoted to precinct captain by the time season 8 rolls around, which probably means she's spending less time out in the field with Castle.

Time will tell on what brings Castle to this decision.

In the mean time, the series is also introducing two new characters, one more prominent than the other. The first is Vikram Singh (Sunkrish Bala), a "high-strung tech analyst with a complicated past" while the other, more important character is Hayley (Toks Olagundoye), a security specialist who will spend a lot of time with Castle in the new season.

Castle season 8 premieres Monday, Sept. 21 at 10 p.m. ET/PT on ABC.

Tags: Castle television ABC