‘Magnum P.I.’ Premiere: Meet Katsumoto’s Partner — and Thomas’ New Girlfriend? (VIDEO)

Private investigator Thomas Magnum (Jay Hernandez) has been going it solo since partner Juliet Higgins (Perdita Weeks) left Hawaii five months earlier. But personally on Magnum P.I., he’s secretly coupled up with tough Honolulu Police Department detective Lia Kaleo (Black Lightning’s Chantal Thuy).

“We’re about two months in so it’s still the honeymoon phase, where things are sweet and tender,” Thuy says. “It’s the good phase of the relationship where you’re still uncertain about how things will develop, but you’re open and open to see.” As for what draws the pair together, Thuy explains Lia likes his compassion, and they “can understand each other because [they] talk the same language.”

One key reason to stay mum: Her partner is Gordon Katsumoto (Tim Kang), who often lectures Magnum over the PI’s not-even-close-to-the-book methods. “The stakes in Katsumoto finding out are higher for her [than for him],” Thuy adds. “Another reason is because it is very hard for women in the police force so that’s also why Lia wants to keep it a secret.”

In the drama’s Season 4 premiere, Kaleo and Magnum unite to find a single mom being pursued by two dangerous mob gangs. Watch an exclusive sneak peek of the case above.

'Magnum P.I.,' 'You,' & More Returning TV Favorites Airing Fridays This FallSee Also

'Magnum P.I.,' 'You,' & More Returning TV Favorites Airing Fridays This Fall

Plus, 'Narcos: Mexico,' and more series to look forward to.

Look for Higgy—drawn back into MI6 work by an operative named Eve (White Collar’s Marsha Thomason)—to return to the island with the October 13 episode. Will she sniff out the hush-hush romance? Says Thuy with a laugh: “We are all detectives, right?”

Magnum P.I., Season 4 Premiere, Friday, October 1, 9/8c, CBS