'Hawaii Five-0' Season 10 Promo: Quinn Liu vs. McGarrett & Danny (VIDEO)

Five-0 is getting a new ally in Season 10.

Katrina Law joins the cast of Hawaii Five-0 this season, and she debuts as Quinn Liu, a former Staff Sergeant with Army CID in the premiere, "Ua 'eha ka 'ili i ka maka o ka ihe." (That's Hawaiian for "The skin has been hurt by the point of the spear.")

Executive producer Peter Lenkov teased, "viewers are going to love seeing how she first encounters McGarrett and Danny," and the premiere trailer offers a look at her facing off with the two men.

All three pull their guns, and Danny (Scott Caan) has a suggestion for Quinn: "If you're going to shoot anybody shoot him," gesturing to his partner.

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Katrina Law Helps the 'Hawaii Five-0' Team in the Season 10 Premiere (PHOTOS)

Law joins the cast as a new series regular, Quinn Liu.

Watch the trailer below to see what else is coming the team's way, including who's going to be involved in a shootout.

In the premiere, a new ally helps McGarrett (Alex O'Loughlin) and Five-0 when mob bosses on the island are being targeted by an assassin. Plus, the team says goodbye to one of their own. Rob Morrow guest stars.

Hawaii Five-0, Season 10 Premiere, Friday, September 27, 8/7c, CBS