My partner just went through another short bout with paranoia and it was scary for him to feel like a all these people out in the world had bad intentions for him and wished him harm. He saw a psychiatrist and got some much needed rest and started taking Respirdal. The thoughts went away but I know they are still a worry as he's developed a heightened sense of security around the house but nothing too extreme. He no longer believes he's being watched or followed. This has happened a few times folllowing a lengthy manic period where he wasn't taking good care of himself. Sleeping, eating and abstaining from alcohol are all immediate steps to take. Also, a darkened bedroom to rest where you feel secure.
The good news is the cars and people in this case were 100%'real and he wasn't "seeing things." His thinking errors were believing that these strangers were malicious and out to harm him.
I hope this passes quickly and you have loved ones available to help you through it.

Sent from my iPhone using Tapatalk