'Asterix the Gaul' was the first adventure in which we met Asterix and the other indomitable Gauls. Their village has managed to hold out against the might of the invading Roman army even after the rest of Gaul had fallen. We learn that their success is due to a magic potion brewed by their druid giving them superhuman strength for a period of time (several hours). We also find out that Obelix fell into a cauldron of the magic potion as a baby and ever since it has had a permanent effect on him.
In this adventure the Romans send a spy to find out what the Gauls secret is. After successfully finding out about the magic potion the Romans manage to kidnap Getafix the druid in an attempt to extract the formula. Asterix goes off to the rescue and with the aid of a special potion from Getafix they confound the Romans and escape from a very hairy situation.
Asterix's next adventure is 'Asterix in Spain'.