Another rash of thefts from vehicles and related crimes hit several Suffolk neighborhoods this week, but unlike many such incidents before, this time people were arrested and charged.

What made the difference? An alert homeowner, who happened to notice suspicious activity at about 4 a.m. on Wednesday and sound the alarm to police.

The crime works like this: a group, usually young people from neighboring jurisdictions, comes intending to steal. They hit a neighborhood and fan out, checking car doors, and rifle through every vehicle that is left unlocked. They steal electronics, firearms, credit cards and more — anything that can easily be sold for cash — as well as any cash itself. If an extra set of keys is left in the vehicle, sometimes they’ll steal the vehicle itself.

It’s one of the simplest crimes to commit, which means it’s also one of the simplest to prevent. It takes almost no time at all to lock your vehicle doors and keep valuables out of sight, and doesn’t require any expenditure of money or effort. And yet it’s surprising that so many people don’t take this small amount of time to protect one of their most expensive possessions.

It’s not just about your car and what’s in it — it’s a matter of public safety.

The reasons to lock the doors to your vehicle don’t end with the possible theft of valuables left inside. Leaving doors to a vehicle unlocked could lead to entry to your home if there is a set of house keys or a garage door opener in the glove compartment. This could lead to the theft of even more valuables and jeopardizes the personal safety of your family.

In addition, leaving vehicle doors unlocked frequently leaves the open invitation to future crime in your neighborhood. Criminals do share information, and word will get around if your neighborhood is known as a good place for theft. You can do a lot to help keep your neighborhood safe just by pushing a button.