Lowther's early history is not well documented but his pirating career began when he served as second mate on the Royal African Company ship Gambia Castle. Along with the standard crew of about thiry men, there were also soldiers commanded by John Massey. These soldiers were being ferried to man a fort which was recently destroyed. Both Lowther and Massey ran into trouble at their destination, and soon Lowther, Massey, and most of the crew seized the ship from Captain Charles Russel. Lowther spoke to the crew and told them that they could no longer safely return to England because of their actions and instead they should seek their own fortunes at sea. The Gambia Castle was renamed Delivery and she was modified into a pirate ship and now manned by some 50 men. Articles were drawn, signed and sworn onto the Bible:

1. The captain is to have two full shares; the master is to have one share and a half; the doctor, mate, gunner, and boatswain, one share and a quarter.
2. He that shall be found guilty of taking up any unlawful weapon on board the privateer, or any prize, by us taken, so as to strike or abuse one another, in any regard, shall suffer what punishment the captain and majority of the company shall think fit.
3. He that shall be found guilty of cowardice, in the time of engagement, shall suffer what punishment the captain and majority of the company shall think fit.
4. If any gold, jewels, silver, etc. be found on board of any prize or prizes, to the value of a piece of eight, and the finder do not deliver it to the quarter-master, in the space of 24 hours, shall suffer what punishment the captain and majority of the company shall think fit.
5. He that is found guilty of gaming, or defrauding another to the value of a shilling, shall suffer what punishment the captain and majority of the company shall think fit.
6. He that shall have the misfortune to lose a limb, in the time of engagement, shall have the sum of one hundred and fifty pounds sterling, and remain with the companymas long as he shall think fit.
7. Good quarters to be given when call'd for.
8. He that sees a sail first, shall have the best pistol, or small-arm on board her.

In June 1721, the new pirates began their plundering of vessels in the Caribbean. On one occasion off Hispaniola, Lowther came alongside a French sloop filled with wine and brandy. Massey boarded the sloop acting as though he was a merchant haggling over the prices. Once the game grew tiresome, Massey whispered to the captain that they would take it all for free. The French captain understood his meaning and the pirates unloaded thirty casks of brandy and five hogsheads of wine among other valuables. Lowther returned five pounds to the French captain "for his civilities."

While they continued to plunder, Massey wanted to attack the French colonies on the land to add to the plunder since he was a foot soldier not a sailor. Lowther and Massey continually argued over the idea until finally it was brought to a vote by the crew. Most of the crew sided with Lowther so Massey was not pleased by the outcome. When Lowther captured, among others, a small sloop in the following days Massey declared he wanted to leave. Lowther was all too happy to rid himself of the nuisance and permitted Massey and his followers to have the sloop as a prize and part company. (As a sidenote, John Massey was eventually hanged in England in 1723 for piracy.)

After many other subsequent plunders, Lowther met up fellow pirate Edward Low and his crew of about a dozen while Lowther was enroute to the Bay of Honduras. Low and his crew joined the larger Lowther pirate crew on board his vessel while Low's smaller one was sunk. In January 1722, Lowther stumbled upon the 200 ton merchant Greyhound and after an hour long running battle, Greyhound eventually surrendered. Before setting fire to the ship, Lowther's crew proceeded to beat and torture the crew. Several other vessels were taken soon after and a few sloops were taken as consorts.

The pirate fleet found a secluded area to careen in the Gulf of Matigue but during this extremely vulnurable time, a large band of natives attacked and the pirates hurriedly fled on the sloops while Happy Delivery was set afire. Lowther moved his command ship to the largest sloop, Ranger of 10 guns and 8 swivel guns. While heading north to the American coast several other vessels were taken and on May 28 they took the brigantine Rebecca. Edward Low decided to part company at this time and the crew were split between the two men, 44 men went with Low on the captured brigantine and 44 remained with Lowther on the sloop.

While off the coast of the Americas, Lowther was able to plunder several small vessels easily but most were not too valuable. One English vessel off South Carolina though did put up a fight that would cost Lowther. To the suprise of Lowther, the vessel Amy did not surrender at sight of the pirates but instead fought back fiercely. Lowther's sloop ran ashore to escape the attack and eventually Amy moved on after their captain was killed. Lowther's loss of crew and damage to the ship was great, so they set sail for North Carolina and eventually spent the entire winter there in the woods.

When spring 1723 arrived the pirates set sail again plundering small prizes near Newfoundland Banks and by August were again roaming in the West Indies. In October 1723, Lowther beached his sloop to careen on an uninhabited island northeast of Tortuga. The sloop Eagle, captained by Walter Moore, traveled past the island on its journey and sighted the careening sloop. Knowing the island was not a typical stop for law biding merchants, Moore investigated the sloop believing it to be a pirate vessel. Moore fired a shot demanding the unknown vessel show her colors and at that, Lowther rose St. George's flag and fired back at the oncoming sloop. With such a hostile reaction, Moore fired back at the sloop until the pirates surrendered. Lowther and about a dozen crewmen escaped out the cabin windows before being captured. Moore sent 25 of his men to search for the missing pirates but only five were caught in the following five days, not including Lowther. Moore set sail with his prisoners and the pirate sloop and after reporting the incident a sloop with 23 men were sent out to find the remaining men hiding in the woods. Four more men were captured but Lowther and three other men and a boy were still missing.

It is said that Lowther's body was eventually found sometime later with a pistol wound and his pistol at his side. So in the end, Lowther escaped the typical pirate's end when he took his own life (rare for a pirate) and with it was the end of the cruel and barbaric tortures he was known for inflicting.