Clues (5)

The two police officers went ahead and did their rounds by checking the library. When they came up to the second floor right where Lucien and Keith is, the two hastily climbed up to the top of the stairs in order to not be seen by the officers. 

They flattened their body like a dough and persistently stick their cheeks into the cold wooden floor. The police officers moved on and wanted to go upstairs but they receive a summon from their walkie talkie. 

It seems they are needed to ransack some place. 

The two police officers glanced at each other before staring at the third floor. 

"We can go back and finish the rounds later." 

"Yeah." 

Then they went out.

Lucien and Keith waited by counting their breath before jumping down from the top of the shelves. They looked at each other before they head towards the top most floor.