Harker had been tipped off by one of the bodyguards that Mina has been spotted around the club districts lately. It seems whatever lead she had about her parents' killers, it had led her into constant bar-hopping and clubbing.
She hasn't returned for two weeks now, and Harker feared that her time as a human was running out soon. If she doesn't get constant SS cells and RH null blood, she'd turn back into a mermaid. It's too dangerous for her to go out on her own under these circumstances even when he could understand her purpose.
"Just where in the blazes are you, Mina….. I'm pretty sure I saw you here just now." He mumbled to himself as he searched the area with his refined snake eyes and body heat sensor.
Even though she was transformed, Harker had noticed that Mina's body temperature was still very slightly lower than an average human. It was a very minor difference, but still pretty important. He put all his focus on sensing her in this area.