The new goau'ld is Anubis, and he looks kinda cool under a hooded cloak. You don't really get to see his face, I thought I did and he looked watery, but it's played by a different character to Apophis so I don't think it's him.
In the episode after an initial section where Sam is struggling to overcome Daniel's possible death/ascension we are shown Thor warning Osiris that she is approaching a protected planet and such behaviour will not be tolerated. After a short exchange of words Thor's ship opens fire on the mothership, but the new shields leave it undamaged. Then the SGC are contacted by Freia. Thor has been captured by Osiris and is being held on the ship. They want SG-1s help to rescue an Asgaard scientist on the planet surface. O'Neill agrees to take part in this mission and they dispatch their cloaked Goau'ld cargo ship. After a turbulent landing on a planet with harsh atmospheric conditions SG-1 are transported into an underground research facility. Jack communicates by the hologram pad with Thor and alerts him that they are trying to rescue him. Thor assures O'Neill that he would die before revealing Asgaard secrets.
The Asgaard scientist reveals to SG-1 that all Asgaard are in fact clones. They lost the ability to sexually reproduce 1000 years ago. The standard of copies is falling and they are dying out slowly as a race. An Asgaard ship from a long time ago crashed on the planet and one crew member, who represents a more genetically pure era of their history is preserved by cryogenics. All, including frozen alien, are transported to the cargo ship.
Anubis travels to Osiris' ship to conduct an interrogation. As he rings across O'Neill and Teal'c also ring in (the Asgaard transporters cannot work through the shields). The aim to cause the shields to fail allowing Thor and SG-1 to be transported to safety. As they search the ship, guided by Sam and the Asgaard scientist they are discovered by a Jaffa patrol. The holographic Sam acts as a decoy allowing them to escape, but Osiris is alerted to their presence on the ship and orders toxic gas, which renders everyone on certain levels, unconscious, at the cost of many trapped Jaffas lives in the engine room, as the engines are made to overheat. Two of the three Goau'ld ships depart for a battle with Lord Yu. Teal'c and O'Neill are locked in a holding cell but left unguarded (overcomplacency always gets it). Thor who has been linked using new goau'ld technology to the ships computer, in the hope of downloading his knowledge, uses this to his advantage and frees Teal'c and O'Neill. Unarmed they try again to power down the shields. Sam left alone in the underground facility communicates instructions to Jack and Teal'c to use the control crystals and shutdown the shields. She is spooked by something in the facility and collapses leaving Jack and teal'c to decide which crystals to pull. It turns out Osiris had located the position of the lab. Acting all smug she says the rest of SG-1 have been captured, and asks the location of Daniel Jackson. Sam after being attacked with the hand device says that he is dead. Jack and Tea;'c obtain staff weapons from an incompitent squad of Jaffa through hand to hand combat!?!?!! They shoot the control crystals and the shields go offline. All of SG-1 and Thor are trasported to the cargo ship. As the cargo ship leaves the atmosphere Thor says they must leave him behind as the link to the Goau'ld ship will give away their position. Sg-1 reject this idea and are shot at as the emerge. Hyperdrive and then the cloaking go offline. Anubis orders them to surrender. The scientist says they must destroy the ship to avoid the Goau'ld obtaining the research. But three vastly superior Asgaard ships commanded by Freia arrive and protect the cargo ship. Anubis' ship (presumably with Osiris on it, though you never see her leave the planet) retreats. I can't think why the Asgaard wouldn't shoot it! The remaining 5 minutes is spent in the SGC with Jack, Teal'c and Sam planning some socialising. A wind blows past Sam and she wonders what it was. Teal'c suggests a fault with the air conditioning. As Jack boards the lift to the surface his hair blows and he turns and smiles, you are left feeling as if Daniel is watching over them.