The scene looks kind of like it's out of order. The dart scene at the end is a flashback to the capture.
I believe the drug they injected her with is truth serum, but it has a sort of sleepy effect.
Sheena doesn't actually die in the end, she fakes her death.
From 3 Volume Thriller/Conspiracy Series Tatiana K. Story by Francois Corteggiani, Drawings by Felix Meynet, Colors by Enrico Marini.
Alternate title: Tatiana K