Teddy realized that when he left earlier he hadn't had time to lock the door to Luci's flat. Therefore he returned to her flat to lock it.
"Argh, how could I forget anyway? Hopefully, Luci's neighbors don't know that the door is unlocked. Because if they find out, they could hurt her by sneaking into the flat," Teddy whispered as he drove his car.
Luci's slum alley was visible. Teddy swooped in and turned to get inside. After arriving at the yard, he immediately got out of the car and then went to the second floor and locked the door to Luci's room.
Teddy knew where Luci kept the spare key. That's why he chose to return to her flat and locked her door.
His footsteps had just stepped on the flat yard until they finally had to be stopped because his eyes found a man he had just met so far.