Later, Jackson briefs Hammond, Dr. Fraiser and the rest of the Stargate Command brass on how his grandfather, Nick Ballard, found the crystal skull. As the story goes, Nick always claimed the skull teleported him to an alien world. The experience drove him out of the scientific community.

SG-1 goes to the planet to retrieve the skull. They head down the narrow walkway to the middle where they find the artifact atop the platform. While the team explores the area, Daniel peers deep into the crystal eyes.

Only Teal'c notices that Daniel is entranced because Carter suddenly picks up a series of radiation spikes emanating from the skull. Teal'c, always the voice of quick action, blasts the object.

The radiation has reached dangerous levels. Carter faints. Jack grabs her and he and Teal'c sprint for the gate, leaving Daniel unconscious on the floor.

Upon returning to Stargate Command, the team quickly lose consciousness. When they awaken, we find them in the infirmary, suffering from radiation poisoning.

Teal'c, less deeply affected by the radiation thanks to his alien symbiote, sits up in bed and tells Dr. Fraiser that Daniel was enveloped in an energy cloud from the crystal skull.

After a short discussion, General Hammond allows Teal'c to go back to get the skull in an attempt to locate Daniel. Unfortunately, when Teal'c starts packing the skull for transport, Daniel regains consciousness -- but his friend is still oblivious to the archaeologist's invisible presence. Instead of heeding Jackson's cries, Teal'c simply grabs the skull and returns to Earth.

Jackson follows, only to find that nobody will acknowledge him. He sees that Carter is still unconscious, while O'Neill is cranky but weak.

As luck would have it, SGC scientist Robert Rothman is assigned to study the skull, despite Jack's protests that "Rothman couldn't figure out an ashtray." Even General Hammond quickly grows frustrated with Rothman's limited powers of creative investigation, while Carter finally gives up and takes over the research project herself after her hapless colleague states that the object is probably a "paperweight."

Meanwhile, Daniel seeks assistance from that time-honored refuge of the invisible, the religious practices of others. He tries to talk to Teal'c while his friend is meditating. This time, Teal'c manages to sense something, even though he's not sure what it is.

As the search for Jackson continues, Hammond decides to launch a UAV (a flying MALP) to look around the pyramid, but refuses to send another SG team until learning more about the situation.

Carter suggests finding Jackson's grandfather to help them with the skull. Fraiser tells them that she has done some checking and Nick Ballard is in a mental institution.

Daniel, now undetectable, takes this opportunity to let his teammates know that his grandfather is insane.

Undeterred, the members of SG-1 arrive at the hospital to meet Nick Ballard. He tells them a rambling story about how Daniel is actually the insane one in the family and that Nick lost everything over his theories that the great pyramids were actually alien landing sites.

However, when Jack announces that they've found another crystal skull, Nick becomes very interested. He promises he will reveal what he knows if the team brings him back to the site.

Hammond is resistant to the idea of bringing Ballard to the SGC, but Jack eventually convinces him.

Nick relates his experience of the cavern, spinning out a bizarre tale of giant mist aliens who spoke to him in extraterrestrial gibberish that translated into "the enemy of my enemy is my friend."

The team sets Nick up in style in the VIP suite while Rothman complains about how little meeting the old man has advanced their research into the skull.

Meanwhile, Daniel figures out that the skull was trying to send him somewhere and they need to go back and find these misty aliens.

After another round of pointless questioning, Nick is left alone in his room. He confesses his sorrow at not being there for Daniel and -- shockingly -- looks straight at his grandson to ask for forgiveness.

Daniel excitedly asks Nick if he can see him. He replies yes, but as it turns out he has been laboring under the conviction that Jackson is a hallucination, so he has not told anyone. They go to Hammond and O'Neill.

Needless to say, they remain dubious, but Nick relays classified information about the stargate and Hammond's private conversations, convincing them.

SG-1 goes back to the pyramid to complete the process Teal'c interrupted by shooting the skull. Nick accompanies them, having weaseled his way onto the squad "according to Daniel's instructions."

Once he gets to the cavern, the old man recognizes the place immediately.

He replaces the skull on the platform and invisible Daniel stares into its eyes, but this time the process continues uninterrupted. Light particles begin to stream out of the skull, bouncing around the room.

Suddenly, Carter, Jack and grandpa go out of phase, where they can see Daniel. Teal'c, left behind, goes back to the base.

A great mist arises from the deep, containing a giant figure that looks like a genie. The figure repeats the "Mayan"-alien phrase, "the enemy of my enemy is my friend."

Daniel figures out that this must refer to the Goa'uld as their enemy, which is why Teal'c -- who contains a larval Goa'uld parasite -- was not brought across. He exclaims that they are also enemies of the Goa'uld and the giant mist alien welcomes them.

He asks them to leave Nick as an emissary as he has been here before. With the touching farewell between a grandson and his now-vindicated grandfather, the episode ends.