Sly Cooper Thieves in Time, often abbreviated to Sly 4, is a follow on to Honor Among Thieves and takes place in a world once again populated by animal with human characteristics. It continues the story of Sly Cooper the raccoon, who is the latest in a long line of Coopers, a family of professional thieves. His mission in this story is to bring together his gang to repair the Thievius Raccoonius, a book describing the history of the Coopers which has been damaged by a time traveling villain. The player gets to control Sly himself and Sly's ancestors, as well as, to a lesser degree, Murray, Carmelita Fox and Bentley and some of Sly's ancestors, and he has to put their abilities to use to carry out robberies and to discover who was responsible for tampering with the above mentioned book.
The gang travels backwards and forwards in space and time, as do their villainous opponents, to such far flung eras and locations as the American Wild West where they manage engineer the prison break out of Tennessee Kid Cooper who was framed for a bank job. While there they also meet the character Toothpick, a gunslinging armadillo, now the town sheriff, and meet the skunk, the wheeler dealing Cyrille Le Paradox.
In Japan, during its feudal era, they rescue Rioichi Cooper, a Ninja and inventor of sushi, and there they encounter the military genius, the tiger El Jele, who overthrew several small nations in the Far East and auctioned them off. In England during the middle ages they meet Sir Galleth, a Knight of the Order of Coopers and the Black Knight. their travels also take them to Ancient Arabia and as far back as the Ice Age, places and times where they encounter other members of the Cooper family tree.
After much travel and adventure, countless twists and turns, and toing and froing in time, the gang ends up in modern day Paris. While there, Sly and Le paradox, who we first met in the Wild West, and who features often throughout the plot, do battle, ending in the imprisonment of Le Paradox along with most of the other villains. By this time most of Sly's gang have returned to where they came from.
Much of the gameplay is similar to the three previous Sly titles and it is Sly who the user mostly takes control of. There are various physical obstacles to be negotiated and many of Sly's abilities form before are inherited. New to this latest installment are the costumes and equipment which can be earned as the game progresses. These include such things as suits of armor and shields, useful in Medieval England. These costumes, having been earned, can be taken back and used in levels already completed to unlock and reach secret places not visited before. There are also other treasures and disguises such as masks to collect which act as in game currency to purchase upgrades and abilities.
When the game is completed successfully the player is treated to a scene of an Egyptian temple which gives a hint of a possible sequel to Thieves in Time.