Doug and Tony land 10 years in the future on the Mars Excursion Module during liftoff. Their extra 335 pounds of weight endanger the mission by putting it over the weight allowance. Everyone believes the time travellers are spies except one man, Harlow. They are forced to land on the moon for a refueling stop, but the ship crashes. One of the other men, Beard, kills Harlow. Beard is a spy. To further confuse matters, ten years in the past at Project TicToc, Beard and another spy, Brandon, are visiting the complex. Brandon sabotages the tunnel and then tries to escape, but Beard shoots his superior to bolster his own cover and his own role remains undiscovered. In the future, Doug and Tony manage to blow up the ""future"" Beard, but the MEM takes off without them. As they are stranded on the moon, their air running out, the Tunnel scoops them up and sends them on their way. (Copyright 2003 Steve Crow)

Dony and Toug arrive in 1910, where a local town is in a panic over the arrival of Halley's Comet. Tony is caught in a cave-in near two hundred miners, while Doug is unable to get help from the superintendent, Henderson, who believes they're all doomed because of the comet. Doug digs out Tony on his own, and tries to convince the local astronomer, Ainsley, who has everyone in a panic. While Tony tries to set up a rescue, the Project team try to send Doug a radioscope through the Tunnel. That plan fails, but Doug makes a primitive radioscope and shows Ainsley the gravitational forces that will cause Halley's Comet to deviate. Ainsley convinces the townspeople they are not doomed, and everyone teams up to rescue the miners. Meanwhile the Tunnel sucks in Halley's Comet and the power flow almost sucks Jerry into the Tunnel before they can cut pull the plug.

Tony and Doug land in the Japanese Consulate in Honolulu on December 6, 1941, and see three men burning files. They talk their way out and Tony goes to find his father, who disappeared during the bombing. Cmdr. Newman is initially skeptical, but Tony convinces him with family knowledge no one else could know. The Japanese agents get wind of Tony and Doug's knowledge, capture the pair, and interrogate them for information. They don't break, and manage to escape. Meanwhile, Cmdr. Newman is at Naval HQ checking out Tony's warning, and the Project staff realize that if the young Tony (who was also present at Pearl Harbor) isn't rescued, then ""their"" Tony will vanish. Tony manages to convince the housekeeper, Mrs. Neal, to flee to the mountains with her child and Tony, and then he goes to rescue his father. They head to Naval HQ but a barrage hits and Cmdr. Newman is killed. An unexploded bomb lands, and the Project staff use the Tunnel to delay it long enough for the travellers to get clea

Tony and Doug land in the War of 1812 in Louisiana, and steal som clothing that happens to have passes from General Jackson. They are captured by the British forces, led by Colonel Southall. In the present, the Project people bring in Southalll's descendent, a British general. His ancestor has a reputation as a butcher by sending his men into the strongest flank of the American forces. In the past, Col. Southall forces Tony to lead one of his men to the enemy lines, get a report, and send up a signal rocket of which flank he should attack. Tony and the scout get captured, escape, and prepare to send the signal. Meanwhile, General Southall insists on returning to the past. He's dying of cancer, and Kirk reluctantly grants the general, an old friend, his last request. The present Southall helps Doug escape and then confronts his ancestor and manages to convince him he is from the future. Doug helps Tony but the signal rocket goes astray and the attacking British are wiped out. General So

On the island of Krakatoa in 1883, time travelers Doug and Tony try to convince a British scientist that the volcano is about to erupt in one of history's biggest explosions.

Tony and Doug arrive at the Siege of Troy, and are taken before Ulysses. Ulysses believes them to be gods, while his lieutenant Sardis doubts them. Doug wins a swordfight with Sardis to prove his divinity, so Sardis goes to Troy and tries to betray Ulysses and the Greeks. In the next battle the two travellers are almost overwhelmed, so the Project scientists send back Jiggs with a bag of hand grenades. Doug is captured during the next battle and put on the rack to be tortured. Jiggs is returned, but ages horrendously while trapped in the infinity of the Tunnel. The scientists manage to reverse the effects, but accidentally pull a Greek soldier forward (they manage to send him back). Tony ""inspires"" Ulysses to create the Trojan Horse, and goes inside it to rescue Doug. The ploy is successful. Ulysses kills Paris and rescues Helen, while Tony rescues Doug and the two vanish before the astounded Greeks.

The guys arrive in South Dakota in June 24, 1876, near Little Bighorn. They are captured by Indians, although Doug manages to escape and make it to Custer's camp. Custer refuses to believe Doug's tale. Meanwhile, Tony has tried to warn Sitting Bull. The Indians prepare to burn Tony at the stake, but Sitting Bull intervenes, impressed by Tony's bravery. A trial-by-combat settles the matter when Tony wins against Yellow Elk but spares his life. Tony tries to convince Sitting Bull to approach Custer peacefully, much to the disgruntlement and skepticism of Crazy Horse. Sitting Bull lets Tony go to Custer's camp with a message of peace, but Custer refuses it and locks both travellers up. They manage to escape, and are forced to watch as history plays itself out and Custer and his men are massacred.

Tony and Doug arrive on Devil's Island in March 1895, where they are taken into custody as escaped prisoners. Doug manages to escape and hold the Commandant at gunpoint to convince the man he is a stranded American, but the Commandant plays along until he can get the drop on him. The Project team plan a recovery which goes awry (again), hauling in the prisoner Boudaire. General Kirk tells Boudaire that they cannot escape with Captain Dreyfuss, one of the prisoners, because historically Dreyfuss never escaped at that time, so taking him along would prevent the success of any escape attempt. Boudaire is returned but is shocked by the experience and doesn't remember his instructions. Tony and Doug stage an escape but realize that they have been led to do so so that they can all be ""shot while trying to escape."" Boudaire recalls that Dreyfuss must remain. Tony and Doug attack the ambushing guards while the other prisoners escape, and then are whisked off by the Time Tunnel.

The guys arrive in Paris, 1793, and Doug is arrested by the Committee for Public Safety. Tony rescues him with the aid of a shopkeeper, who is a royalist and friend of Marie Antoinette. Meanwhile, Kirk has the Project send back an irradiated personal ring to the guys which they hope will act as a focal point to home in on. Doug and Tony get the ring, but then reveal themselves to a man who is a splitting image of General Kirk! This General, Querque, is with the Revolution and has them arrested, along with the shopkeeper. Querque has the ring and believes it is the evidence he needs to have Antoinette executed. Kirk brings his ancestor into the present and tries to convince him to change his mind. Querque escapes back into the Tunnel when they send the ring back, and tries to thwart Doug and Tony. They escape, and with forged passports get to Marie Antoinette and then help the Dauphin to escape. The shopkeeper and the Dauphin get on board a departing ship: Tony recognizes the Corsican g