According to The Hollywood Reporter, the show will introduce Janssen on its May 5 episode. Details are being kept quiet, but she'll play Susan "Scottie" Halsted, possibly the mother to series regular Ryan Eggold.
From there, the spin-off pilot is expected to air May 12, with showrunners Jon Bokenkamp and John Eisendrath serving as writers. More casting should be announced soon, and it's likely familiar faces from the flagship will join.
It's no surprise the network is considering a spin-off: The Blacklist has served as one of NBC's best-performing series since its 2013 debut. It's NBC's second-ranked drama after Blindspot. While it's currently unclear if the spin-off will be planned for the 2016-17 season, a decision is expected within the next few months.
UPDATE: Deadline reports that Edi Gathegi, who first made his debut on The Blacklist earlier this season, will join the spin-off as a series regular should it go to series, along with Ryan Eggold.
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