A fortnight is long enough for home scent to fade from a coat and for cattery smells to take its place. Your resident cat reads that changed smell before anything else, so a cat who shared sofas happily last month may greet the returner with flattened ears, staring or a hiss at the carrier. None of that means the bond has gone. It means the first meeting needs to be rebuilt in layers, starting with scent and ending with shared space only when the earlier layers look calm.
Start With Scent, Not a Reunion
Keep the returning cat in one quiet room on arrival, with a tray, water, food and a bed of its own, and let the resident cat stay in the rest of the home. Rub a soft cloth gently over the returner's cheeks and chin, then leave that cloth near the resident cat's resting place, and do the same in reverse with a cloth carrying the resident's scent. Swap their bedding over as well, so each cat sleeps on material that smells of the other. Watch what happens around those cloths: sniffing, rubbing a cheek against them or simply ignoring them are relaxed responses, while backing away, growling or leaving the room tells you to stay at this stage longer.
Feed Either Side of a Closed Door
Once scent items no longer draw a reaction, serve meals on opposite sides of the door between the two cats, far enough back that both eat without staring at the gap under it. Eating near the sound and smell of the other cat pairs that presence with something each cat values. Move the bowls a little closer to the door across successive meals only while both cats keep eating normally. A cat who walks away from food near the door is giving clear information, so return the bowl to the previous distance and hold there for another day rather than pressing on.
Add Sight, Then Short Shared Time
When door feeding looks easy, open the door onto a secure barrier such as a stacked baby gate or a door held ajar on a latch, so the cats can see each other without touching. Keep these sessions brief, scatter treats on both sides, and end them while both cats are still relaxed rather than after tension builds. Then allow supervised time in one room, with an exit route open for whichever cat wants to leave, and separate them again at the first hard stare, chasing or cornering. Lengthen shared sessions gradually, and keep separate trays, bowls and resting spots available until the pair are choosing to rest near each other, eating side by side without guarding, and moving around each other with loose, ordinary body language.
Judge Progress by Behaviour, Not the Calendar
Progress may be quicker than a first introduction between strangers, because these cats already have a shared history, shared routines and familiar sounds to fall back on. Treat that as a tendency, never a guarantee: a confident returner and a sensitive resident can still need a slow week, and rushing the final stage is what turns a mild hiss into a proper falling-out. If either cat stops eating, hides for long stretches or starts avoiding the tray, drop back one stage for a couple of days and build up again. A fight with fur flying or any bite wound means full separation, a fresh start at the scent stage, and a vet check for the wounded cat.
Shared stages go more smoothly when each person in the house knows which step the pair has reached and what not to skip. Recording the current stage in Care Teams within KinsLe, with the next step assigned to whoever is home, stops a well-meaning family member opening every door on day one.