I believe the problem will be a loose, and possibly now burnt wire connection at one receptacle.
I usually find this at the last working outlet on the circuit before the outlets that have no power, or the first non working outlet before all the others that are not working.
Back in the 70's, it was popular to use connections at outlets that the wire is plugged in, pushed into small holes on the back of the receptacle. This type of connection has several names,Whiz Wire, Quik Wire, Stab in the Back, etc.
Unfortunately, some electricians still do this type of connection nowadays, esp in subdivision homes that need to get built quick and for cheap. Devices are now made better to help prevent this problem, but it still happens.
These are very prone to loosening. Can be either the hot or neutral wire.
The use of a heater can exasperate this connection, making it worse, and will cause heat at the connection, burning the connection even more.
To find this bad connection will take knowledge of how the circuit is wired, which outlet is the last working outlet or the first non working outlet. You will also need to know which circuit breaker supplies this circuit, as even thou an outlet is not working, it can still have power inside, so each time you pull out an outlet, shut the breaker off.
Only turn on the breaker to test the wires with a voltage tester or meter.
To do this testing, I would not waste my money on a plug in tester, but one with test leads. All a plug in tester will tell you is that the outlet is not working properly, which you already know.
Be prepared to change the outlet that has the bad connection, electric heaters are popular to cause heat at loose connections, and if this is the case, the outlet with the bad connection may be damaged.
As you pull out outlets looking for the bad connection, it may be wise to change any push in connection to wrap around the screw connection, as handling the outlets and wires can cause more loose connections.
There maybe a chance that the outlets only allow push in connections, there were some cheap outlets installed that don't have screw connections on the sides, only push in the back type.
If you have the skills to work with wires and outlets, and figure out how the circuit is wired, you should be able to find this problem.
Just be sure to shut the breaker off while handling outlets and wiring, only turning on to test wires and outlets.
The bad connection can be a splice also, more likely the push in connection, but anything is possible.
If you do end up needing to call in an electrician, he/she should be able to find this problem in less than an hour. Ask how much a service call charge is, and how much time on the job is included in a service call. Be sure the electrician is set up for service, and not just construction. Any electrician that advertises 24 hour service should be helpful, quick, and fair.
Now speaking of Electrical 101, as mentioned by 21Boat, the statement:
PS. The ground and netural is actually the same thing.
is not true.
A neutral is actually a current carrying conductor, that has been grounded to keep any voltage to zero.
A " ground" in circuit wiring, is called an equipment ground, this is the green or bare wire, and is for the purpose of safety, to carry any fault current due to a short circuit from hot to any exposed metal in a circuit, device, applaince, etc.
By allowing any and all fault current to flow, will allow a circuit breaker of fuse to open quickly, and shut power to the circuit, to prevent shocks and fire.