In Security is the sixth episode of the fourth season. It was released on 2 November 2007.
A play on 'insecurity', and the shaking of the bedrock of Charlie's world when his big brother is in serious trouble.
The Wexfords' front door is briefly visible at the start of the episode, and a Mezuzah is clearly visible on the doorframe. A Mezuzah is a small case containing a passage from the Torah (Deuteronomy 6:4-9), which Jews traditionally affix to the door frames of their houses as a constant reminder of God's presence; it also serves as a sign that the residents of that house are Jewish.
The cover of Charlie's book "The Attraction Equation" which is about an equation for friendship and attraction, is similar to the cover of John Green's "An Abundance of Katherines" which is about a teenager who tries to come up with an equation for relationships.
[This appears on the beginning of the episode] 17,000 protected witnesses 10,000 convictions 37 years 0 witnesses killed