I think someone is preoccupied with something, but I can't quite put my finger on it.
Persecutory delusions are a delusional condition in which the affected person believes they are being persecuted. Specifically, they have been defined as containing two central elements:[1]
The individual thinks that harm is occurring, or is going to occur.
The individual thinks that the perceived persecutor has the intention to cause harm.
According to the DSM-IV-TR, persecutory delusions are the most common form of delusions in schizophrenia, where the person believes "he or she is being tormented, followed, tricked, spied on, or ridiculed."[2] In the DSM-IV-TR, persecutory delusions are the main feature of the persecutory type of delusional disorder.
http://en.wikipedia.org/wiki/Persecutory_delusion