Once the camera has panned over to Danger Mouse and Penfold's starting position, you'll have to pick up Penfold and throw him up to a platform; once you've done so, you will have to switch to Penfold, activate his shield, switch back to Danger Mouse, jump up to the platform, pick up Penfold and throw him at a stack of two crates to smash it, pass through an electrical force field, and land on the first step of another platform. You will then have to switch back to Penfold, deactivate his shield (while watching out for toad guard), climb down a ladder, and crawl to the left through a hole in the wall onto a red button to turn it green and invert the position of the electrical force field (killing second toad guard in the process, but if you crawl off it again, it will invert the position of that force field again) - and once you've done so, you will have to switch back to Danger Mouse, drop down to the first step of the second platform, kick the first toad guard three times to kill him, jump back to the left onto a third platform and collect the first "DM" badge. You will then have to retrace your steps back down onto the second platform's second step, switch back to Penfold, crawl back to the right out of the hole in the wall inverting the position of that first force field in the process, climb back up the ladder, drop down to the second step of the platform, switch back to Danger Mouse, pick up Penfold and throw him over a pool of water to land on a fourth platform; once you have done this, you shall have to jump over the pool of water, walk down a staircase, switch back to Penfold, follow Danger Mouse's path, jump onto a vertically-moving platform, activate his shield and deactivate it again once he passes through another electrical force field, jump up to a fifth platform, throw a switch to deactivate the second electrical force field and collect that second "DM" badge. You'll then have to switch back to Danger Mouse, jump onto the vertically-moving platform and a sixth platform in turn, drop down to a seventh platform, jump up to an eighth platform, a second vertically-moving one and a ninth one in turn, and jump up to collect the third "DM" badge - and once you have done so, you will have to switch back to Penfold, follow Danger Mouse's path, switch back to Danger Mouse, pick up Penfold and throw him up to a second staircase. You shall now have to switch back to Penfold, walk up the second staircase to the first step of a tenth platform, drop down to the second step of the tenth platform, throw another switch and unlock two doors (one in front of you, another below you), walk through the first door, drop down to an eleventh platform and collect the fourth "DM" badge; once you've done so, you'll have to drop back down to the ninth platform, a twelfth platform and the first step of a thirteenth platform in turn, walk up a third staircase to the second step of the thirteenth platform, jump onto three clouds in turn, and collect the fifth "DM" badge. You'll then have to jump onto a fourteenth platform, throw another switch to deactivate third electrical force field, drop down to the first step of a fifteenth platform, walk up a fourth staircase to the platform's second step, drop back down to the first step of the platform, walk down a fifth staircase to the third step of the platform, walk up to an air vent to be carried up to a second one upon a sixteenth platform, collect the sixth "DM" badge, while getting carried up to a third one on a seventeenth platform, and collect the seventh "DM" badge while being carried up to an eighteenth platform - and once you've done so, you shall have to switch back to Danger Mouse, walk through the second door, follow Penfold's path up to the eighteenth platform, pick up Penfold, and throw him up to the first step of a nineteenth platform. You then have to jump up onto the first step of the nineteenth platform, walk up a sixth staircase to the second step of the platform and onto second red button to turn it green and deactivate a fourth electrical force field (but for a second time, if you walk off it again it will reactivate it again); once you have done so, you will have to switch back to Penfold, jump up onto the platform's second step, fall down onto its third step, jump up onto its fourth step, crawl to the left through another hole in the wall and throw a third switch to freeze all the water. Once you've done so the two waterfalls to its left and right, along with those two clouds above it, will turn to ice - and it's also worth noting that the frozen clouds will become heavy enough to take Danger Mouse's weight.
You then have to switch back to Danger Mouse, jump onto three frozen clouds and a twentieth platform in turn (reactivating the fourth electrical force field in the process), switch back to Penfold, throw that third switch again to unfreeze all the water again, switch back to Danger Mouse, walk through that (now-unfrozen) waterfall, switch back to Penfold, throw the third switch for a third time to refreeze all the water, jump on another frozen waterfall, two more frozen clouds, a third frozen waterfall and two more frozen clouds in turn, drop down to an eighth frozen cloud, then collect the eighth "DM" badge; once you've done so, you will have to drop down to a twenty-first platform and walk back to the left onto a third red button to turn it green and activate a fourth air vent (but if you walk off it again, it'll deactivate it again). You then have to switch back to Penfold, walk up to the fourth air vent to become carried up to that second frozen waterfall, follow Danger Mouse's path down to the twenty-first platform, walk down a seventh staircase to a twenty-second platform, crawl to the right through third hole in the wall, climb down another ladder to the ground, and collect the ninth "DM" badge - then, once you've done it, you will have to retrace your steps back up to the halfway point of the seventh staircase, jump up to a horizontally-moving platform and collect the tenth "DM" badge. You then have to switch back to Danger Mouse, walk halfway down the seventh staircase, jump onto the horizontally-moving platform deactivating the fourth air vent again in the process, pick up Penfold, and throw him up to the first step of a twenty-third platform; once you have done so, you'll have to switch back to Penfold, crawl to the left through a fourth hole in the wall, drop down to the platform's second step and back down to the twenty-second platform in turn, throw a fourth switch to unlock a third door to your right and walk to the left to the level's exit. You'll then have to switch back to Danger Mouse, drop back down to that twenty-second platform, walk back to the left through that third door and follow Penfold's path to the exit - and the "MISSION COMPLETE!" text shall now appear on the screen for a twelfth time. The duo will then proceed to Episode 13 (which is again set deeper in the Weathertorium, and features thunderous clouds, as well as more water-freezing machines).